No 12180, Tuesday 05 Dec 2017, xChequer

Have to leave early for a medical appointment. Leaving a lot of gaps for commenters to fill.

ACROSS
7   Closely focus on jam consumed (6) FIXATE {FIX}{ATE}
8   Wallop snitches, must scratch lousy tip (3,5) BUMST??? {BUMS}T???  (Addendum - BUMSTEER {B{MUST*}EER} - See comments)
9   Depression in bay, need to track (5,3) BLACK DOG BLACK {DOG} Anno pending (Addendum - {B}{LACK}{DOG} - See comments)
10 Silent comedian hands out fish (6) CAPLIN ChAPLIN

11 Play for some time before high school (5) STALL Anno pending (Addendum - {S}{TALL} - See comments)
12 Alien life, originally evolving from the same ancestor (6) LINEAL {ALIEN+Life}*
14 Expanding corporation merged, deals paid off (6-3,6) MIDDLE-AGE SPREAD*
17 Spoke of diamonds cutting diamonds — nothing very revolutionary (6) VOICED {O}{V}<={ICE}{D}
18 Transmits without beginning, leaving word (5) ADIOS rADIOS
22 Long to wear pope's embroidered, old-fashioned robe (6) PEPLOS {POPES}* over {L} With some help from Google :-)

23 Victories and cheers endlessly spur him to improve (8) TRIUMPHS {SPUR+HIM+To}*
24 Pots possibly break (8) STOPOVER {POTS<=} [RA]
25 Release 10-12 points in record time (6) EXEMPT {E{X}{EM}P}{T} Anno for EM not clear See comments

DOWN
1   Condition lifted with grave remarks for educational outing (5,4) FIELD TRIP {LIFTED*}{RIP}
2   Rip healed, left a scar (6) RASCAL {L+A+SCAR}*
3   Fencing weak end of corral (5) KENDO [T]

4   Kisses knickers reportedly (8) SMACKERS [DD] (Addendum - (~nickers) - See comments)
5   Spots artist blasting helper, he's pocketed tips (8) STIPPLER {heLPER+TIPS}* With some more help from Google

6   Twist Watson's double? (5) ???I? (Addendum - HELIX [DD] - See comments)
8   Touching request from gentle tribe, worried about horse (7,6) BEGGING LETTER {GENTLE+TRIBE}* over {GG}
13 Silver lining from Spooner's fodder in fibrous line (3,2,4) RAY OF HOPE (-h+r)RAY of (-r+h)HOPE
15 Plods away without even looking up, unconcerned with new advances (8) DEVELOPS {D{EVEn<=}LOPS*}
16 Capable of sending out electronic communication (8) EMISSIVE {E}{MISSIVE}
19 Case of one-time silver lining initially detected for every cloud (6) DAMPER {De...d}(ArgentuM}{PER}
20 Champ to the core, setter's full of substance (5) MEATY {M{EAT}Y}
21 Instances of x (5) TIMES [DD]

GRID