Allude in freer usage (5)
I believe the answer is:
refer
'allude' is the definition.
(thesaurus)
'freer usage' is the wordplay.
'usage' indicates anagramming the letters.
'freer' with letters rearranged gives '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" .)