Part of loft or chimney set on fire (5)
I believe the answer is:
torch
'set on fire' is the definition.
(I've seen this before)
'part of loft or chimney' is the wordplay.
'part of' indicates a hidden word.
'TORCH' is hidden in the letters of 'loft or chimney'.
(Other definitions for torch that I've seen before include "Set fire to - hand-held light" , "Such a love song" , "Set alight deliberately" , "source of enlightenment" , "Hand-held lamp or burning stick" .)