At home, sat mock, previously unwilling (10)
I believe the answer is:
'unwilling' is the definition.
'at home sat mock previously' is the wordplay.
'at home' becomes 'in' (similar in meaning).
'sat' becomes 'posed' ('pose' can be a synonym of 'sit').
'mock' becomes 'dis' (both can mean to make fun of or insult).
'previously' says to put letters next to each other.
'posed' put after 'dis' is 'disposed'.
(Other definitions for indisposed that I've seen before include "Slightly unwell" , "Poorly" , "Out of sorts" .)