Allude in freer usage (5)
I believe the answer is:
refer
'allude' is the definition.
(I've seen this before)
'freer usage' is the wordplay.
'usage' is an anagram indicator.
'freer' is an anagram of 'REFER'.
'in' is the link.
(Other definitions for refer that I've seen before include "If special treatment needed, GP might do this" , "Be relevant (to)" , "Make allusion, or turn to for information" , "Allude (to something)" , "Allude, assign" .)