Answer and anno of 16D left for a first time commenter till 10 AM.
Across
6. Stupid fellow, getting caught in the bar (5) DUNCE {DUN{C}E}7. Crash as one becomes old in the west (8) OCCIDENT {(-a+O)CCIDENT}
10. Payment for space, back up on time (7) MOORAGE {ROOM<=}{AGE}
11. Vile, putrid, takes seconds to create mayhem (7) DISRUPT {PUTRID*} around {S}
12. For call girl, sex is money (7) RINGGIT {RING}{G}{IT}
13. Applause — eggs on to get it back (7) OVATION {OVA}{IT<}{ON}
14. Had met a nobleman before in the final (11) ENCOUNTERED {EN{COUNT}{ERE}D}
19. Habit of fool chopping hay (7) CASSOCK {C{ASS}OCK}
21. Stop a book halfway and publish — no bar (7) ABOLISH {A}{BO
23. Dregs that remain around university (7) RESIDUE {RESID{U}E}
25. Railroad only to check delay (7) DRAGOON {{DRAG}[O}{ON}}
26. Use merit to become a don post retirement (8) EMERITUS {USE+MERIT*}
27. Lodging or dislodging tips from photo cell (5) HOTEL {
Down
1. Girl's a cat, did you say? (8) ANNOUNCE {ANN}{OUNCE}2. Writer's fear of losing way in city (6) PENANG {PEN}{ANG
3. Solve problem, Mack's perhaps pining (10) LOVESTRUCK {SOLVE*}{TRUCK}
4. Part of medicals, getting high on drug (4) ACID (T<=)
5. Growth rings will invalidate one (6) ANNULI {ANNUL}{I}
6. Horribly rude with me? On the contrary (6) DEMURE {RUDE+ME*} Semi-&lit
8. Sped away bearing gloom (7) DESPAIR {SPED*}{AIR}
9. Feel bad it's time for lunch (5) ATONE {AT}{ONE}
13. I shouldn't refuse to drink a rum (10) OUTLANDISH {I+SHOULDNT*} around {A}
15. First check how the German makes soup (7) CHOWDER {C
16. Girl without sail, out in the capital (8)
17. Not even once horse gets shade (5) OCHRE {O
18. Phone placed on laptop keeps bugs away (6) PHENOL {PHONE*}{L
20. Oil producer creates a mess close to shore (6) SESAME {A+MESS*}{
22. Choice for pain is a herb (6) ORACHE {OR}{ACHE}
24. Opponents a short distance apart, they’re amphibians (4) EFTS {E{FT}S}
Reference List
Caught=C, One=A, Old=O, Seconds=S, Girl=G, University=U, Only=O
Writer=Pen, Way=St, One=I, The German=Der, Choice=Or, Opponents=ES, Short distance=Ft
Colour/Font Scheme
Definition, Solution, Component letters, Embedded links, Anagram Indicator, C/C indicator, Reversal Indicator, Hidden word Indicator, Letter Pick indicator, Deletion Indicator, Homophone Indicator, Movement Indicator, Positional Indicator, Substitution, Indicator, Link/Connector, Extraneous