Chin-wagging a bit (4)
I believe the answer is:
inch
'a bit' is the definition.
(thesaurus)
'chin-wagging' is the wordplay.
'wagging' indicates anagramming the letters (letters swing or wag around).
'chin' with letters rearranged gives 'INCH'.
(Other definitions for inch that I've seen before include "1/12 of foot" , "Fraction of a foot" , "Not very far" , "One-twelfth of a foot" , "Part of a foot" .)