Lets the sow loose after all (6)
I believe the answer is:
allows
'lets' is the definition.
('allow' can be a synonym of 'let')
'the sow loose after all' is the wordplay.
'loose' is an anagram indicator (letters are loosened from their original positions).
'after' says to put letters next to each other.
'sow' anagrammed gives 'ows'.
'ows' after 'all' is 'ALLOWS'.
(Other definitions for allows that I've seen before include "Grants leave" , "Tolerates" , "Permits, lets" , "Sallow (anag.)" , "Permits to do something" .)