Is trapped in sweltering lift (5)
I believe the answer is:
hoist
'lift' is the definition.
(hoist can mean to lift something up)
'is trapped in sweltering' is the wordplay.
'trapped in' is an insertion indicator.
'sweltering' becomes 'hot' (similar in meaning).
'is' going within 'hot' is 'HOIST'.
(Other definitions for hoist that I've seen before include "Lift using pulley and ropes" , "Elevate" , "Jack" , "One that could raise" , "group of flags" .)