Set fire to rubbish piled up next to church (5)
I believe the answer is:
torch
'set fire to' is the definition.
(I've seen this before)
'rubbish piled up next to church' is the wordplay.
'rubbish' becomes 'rot' (both can mean nonsense).
'piled up' says the letters should be written in reverse.
'next to' means one lot of letters go next to another.
'church' becomes 'ch' (common abbreviation).
'rot' written backwards gives 'tor'.
'tor'+'ch'='TORCH'
(Other definitions for torch that I've seen before include "Link" , "Portable light; burn" , "Small hand-held battery lamp" , "Deliberately set fire to" , "Set fire to (something)" .)