I'm trapped by burning ceiling (5)
I believe the answer is:
limit
'ceiling' is the definition.
(I've seen this in another clue)
'i'm trapped by burning' is the wordplay.
'trapped by' indicates putting letters inside.
'burning' becomes 'lit' (I've seen this before).
'im' inserted inside 'lit' is 'LIMIT'.
(Other definitions for limit that I've seen before include "Furthest bound" , "Restrict - term" , "Breaking point" , "Cap" , "Ration" .)