At home, allow a bay (5)
I believe the answer is:
inlet
'a bay' is the definition.
(I've seen this before)
'at home allow' is the wordplay.
'at home' becomes 'in' ('I'm in' can mean 'I'm at home').
'allow' becomes 'let' (synonyms).
'in'+'let'='INLET'
(Other definitions for inlet that I've seen before include "Small coastal opening" , "One's up the creek here" , "Coastal bay" , "Fjord" , "Entry port" .)