Apply in freer usage (5)
I believe the answer is:
refer
'apply' is the definition.
(I know that apply is a more specific form of the action refer)
'freer usage' is the wordplay.
'usage' indicates an anagram.
'freer' with letters rearranged gives 'REFER'.
'in' is the link.
(Other definitions for refer that I've seen before include "Send or direct to a specialist" , "Make allusion, direct attention with words" , "Relate" , "Fail (an exam candidate)" , "Freer (anag.)" .)