Will mates let loose in temporary accommodation? (9)
I believe the answer is:
testament
'will' is the definition.
('testament' can be a synonym of 'will')
'mates let loose in temporary accommodation?' is the wordplay.
'let loose' indicates anagramming the letters.
'in' is an insertion indicator.
'temporary accommodation?' becomes 'tent' (I've seen this before).
'mates' is an anagram of 'stame'.
'stame' inserted into 'tent' is 'TESTAMENT'.
(Other definitions for testament that I've seen before include "books, with 1a [OLD]" , "Written statement of wishes" , "Statement (anag.)" , "Scripture" , "Will - covenant" .)