A turn performed by a liberal is unaffected (7)
I believe the answer is:
natural
'unaffected' is the definition.
(similar in meaning)
'a turn performed by a liberal' is the wordplay.
'performed' indicates an anagram.
'by' means one lot of letters go next to another.
'liberal' becomes 'l' (abbreviation).
'a'+'turn'='aturn'
'aturn' is an anagram of 'natur'.
'natur'+'a'+'l'='NATURAL'
'is' is the link.
(Other definitions for natural that I've seen before include "Unvarnished" , "Unspoilt" , "Without affectation" , "Unaffected or earthy" , "Unaffected - musical note" .)