Hill by church, source of light (5)
I believe the answer is:
torch
'source of light' is the definition.
(thesaurus)
'hill by church' is the wordplay.
'hill' becomes 'tor' (tor is a kind of hill).
'by' is a charade indicator (letters next to each other).
'church' becomes 'ch' (common abbreviation).
'tor'+'ch'='TORCH'
(Other definitions for torch that I've seen before include "Hand-held lamp or burning stick" , "Deliberately set fire to" , "Set fire to (something)" , "Set fire to; electric lamp" , "Such a love song" .)