Friendly weapon at the Western front (4)
I believe the answer is:
warm
'friendly' is the definition.
('warm' is associated in meaning with 'friendly')
'weapon at the western front' is the wordplay.
'weapon' becomes 'arm' (I've seen this before).
'at' is a charade indicator (letters next to each other) (I've seen this in other clues).
'front' says to take the initial letters.
The first letter of 'western' is 'w'.
'arm' after 'w' is 'WARM'.
(Other definitions for warm that I've seen before include "Tepid" , "easily aroused" , "excited" , "(Of a scent) fresh" , "Pleasantly hot" .)