Freeloader given shelter by companion (5)
I believe the answer is:
leech
'freeloader' is the definition.
(I've seen this before)
'shelter by companion' is the wordplay.
'shelter' becomes 'lee' (I've seen this before**).
'by' means one lot of letters go next to another.
'companion' becomes 'ch' (I've seen this in other clues).
'lee'+'ch'='LEECH'
'given' acts as a link.
(Other definitions for leech that I've seen before include "Worm - sponger" , "Old doctor" , "Freeloader" , "scrounger" , "Old medicinal sucker" .)