Go in with some Aberdeen Terriers (5)
I believe the answer is:
enter
'go in' is the definition.
(synonyms)
'with some aberdeen terriers' is the wordplay.
'with' indicates a hidden word.
'ENTER' can be found hidden inside 'some aberdeen terriers'.
(Other definitions for enter that I've seen before include "Fruit drink" , "Join (for the first time)" , "Go in and put in the ledger" , "Come in - register" , "Register formally as a participant" .)