Parasite finds shelter over church (5)
I believe the answer is:
leech
'parasite' is the definition.
(synonyms)
'shelter over church' is the wordplay.
'shelter' becomes 'lee' (I've seen this before).
'over' is a charade indicator (letters next to each other).
'church' becomes 'ch' (common abbreviation).
'lee'+'ch'='LEECH'
'finds' acts as a link.
(Other definitions for leech that I've seen before include "Old physician" , "Blood-sucking worm or parasitical person" , "Worm - sponger" , "One who sponges on others" , "Proverbial bloodsucker" .)