Freeloader in shelter? Check (5)
I believe the answer is:
leech
'freeloader' is the definition.
(I've seen this before)
'shelter? check' is the wordplay.
'shelter?' becomes 'lee' (I've seen this before**).
'check' becomes 'ch' (I've seen this in other clues).
'lee'+'ch'='LEECH'
'in' is the link.
(Other definitions for leech that I've seen before include "Archaic word for physician" , "Sucking parasite" , "Proverbial bloodsucker" , "Blood sucker" , "Clinging type" .)