Solution to 18A has been deliberately left unsolved and is to be answered only by a non-regular / novice commenter, with proper annotation. Those who have answered earlier in the week, please give others a chance.
Open for anyone to answer, if not solved by 1 PM.
ACROSS
7 Noble lion killed for piece of beef (7) SIRLOIN {SIR}{LION*}
10 Better if solicitor spends time with head of monastery at church (8) OUTMATCH {tOUT}{Mo...y}{AT}{CH}
11 America about to tax entry (6) ACCESS {A}{C}{CESS}
17 Curtsy King and Knight with bare heels (5) KNEEL {K}{N}{hEEls}
18 Bay blowing cold smell (4) R?E?
19 Ruth got cash distributed for having an urgent universal urge for relief (6,5) CAUGHT SHORT*
23 Vigorous Chelsea occasionally occupying space at the top (8) ATHLETIC {AT{cHeLsEa}TIC}
25 Dirty as beer fermented with piece of meat (7) BESMEAR {AS+BEER+Meat}*
26 Second revolt over England withdrawing basic rail support (7) SLEEPER {S}{REP{E}EL<=}
DOWN
1 Tiny men in America, run away from cruel fights (9) MINUSCULE {M}{IN}{US}CrUEL*}
2 Boot past student, possibly out on a limb (6) ALUMNI {ALUMNI+BOOT}*=OUT ON A LIMB
3 Means racket time (4) DINT {DIN}{T}
4 Coy sculler regularly participating in swimming games for unit (10) MEGACYCLES {CoY+sCuLlEr} in {GAMES}*
5 Just not following chapter on B-52 support for ground troops, for instance (3,5) AIR COVER {fAIR}{C}{OVER}
13 Revolutionary British King and Luxembourg Knight plan faceless American supremacist organisation (2,4,4) KU KLUX KLAN {UK<=}{K}{LUX}{K}{pLAN}
16 Manliness? Male suffering, for the most part, is minute and ordinary! (8) MACHISMO {M}{ACHe}{IS}{M}{O}
20 Old boy looked and followed (6) OBEYED {OB}{EYED}
21 Trace quiet communist (5) SHRED {SH}{RED}
24 Dance and haul away (4) HULA*
Reference List
Good = G, Hot = H, Time = T, Church = CH, America = A, About = C, Fifty = L, King = K, Knight = N, India = I, Second = S, England = E, Men = M, Run = R, Following = F, Chapter = C, Puff = AD, Knight = K, Male = M, Minute = M, Ordinary = O, Old boy = OB, Quiet = SH
