Solutions

ACROSS
1 Fight off.
(two meanings)
5 Gallic.
GAL+L+I+C
9 Rearmice.
REAR+MICE
10 Narnia.
NA+RNIA (rain anag.)
12 Evade.
EVAD+E (Dave anag.)
13 Traversed.
TRA+VERSE+D (art rev.)
14 Take for a ride.
(two meanings)
18 Stone-cutting.
(straight cryptic)
21 Adam's wine.
A+DAMS+WINE
23 Bleat.
BLEA+T (Abel anag.)
24 Irises.
IRIS+E+S
25 Sillitoe.
S+ILL+I+TOE
26 Theory.
THE+O+RY
27 Demented.
D+E+MEN+TED


DOWN
1 Ferret.
FE(R+R)ET
2 Go away.
GOA+WAY
3 Temperate.
TEMPERA+TE
4 Face the music.
(two meanings)
6 Aware.
A+W+AR+E (RA rev.)
7 Landslip.
(straight cryptic)
8 Chandler.
C+HANDLE+R
11 Lay on the line.
(two meanings)
15 Annabelle.
ANN+ABEL+LE
16 Essayist.
ESSAY+IST
17 Volatile.
(anag.)
19 Beat it.
BE+A+TIT
20 Attend.
A+T+T+END
22 Steer.