Allow a daughter to join US college (5)
I believe the answer is:
admit
'allow' is the definition.
(admitting is a kind of allowing)
'a daughter to join us college' is the wordplay.
'a daughter' becomes 'ad' (I've seen this in other clues).
'to join' means one lot of letters go next to another.
'us college' becomes 'mit' (I've seen this in other clues).
'ad'+'mit'='ADMIT'
(Other definitions for admit that I've seen before include "Recognise" , "Agree to the truth" , "permit to come in" , "Let in - concede" , "Grant entry to" .)