Hot swinger let loose (10)
I believe the answer is:
sweltering
'hot' is the definition.
(similar in meaning)
'swinger let loose' is the wordplay.
'loose' is an anagram indicator (letters are loosened from their original positions).
'swinger'+'let'='swingerlet'
'swingerlet' with letters rearranged gives 'SWELTERING'.
(Other definitions for sweltering that I've seen before include "getting unpleasantly hot" , "hot and sweaty" , "Hot and humid" , "getting uncomfortably hot" .)