With skill, you can take odd bits off fat belly (4)
I believe the answer is:
ably
'with skill' is the definition.
(I've seen this before)
'you can take odd bits off fat belly' is the wordplay.
'you can take odd bits off' indicates alternate letters (letters in odd-numbered positions removed).
'fat'+'belly'='fatbelly'
The alternating letters of 'fatbelly' are 'ABLY'.
(Other definitions for ably that I've seen before include "With competence" , "In proficient manner" , "With great skill" , "In a competent fashion" , "In capable manner" .)