Pursuing answer, fool had trouble (7)
I believe the answer is:
agitate
'trouble' is the definition.
(agitating is a kind of troubling)
'pursuing answer fool had' is the wordplay.
'pursuing' says to put letters next to each other.
'answer' becomes 'a' (abbreviation eg in Q and A).
'fool' becomes 'git' (both can mean an annoying person).
'had' becomes 'ate' (e.g. I had an ice cream).
'a' put next to 'git' is 'agit'.
'agit'+'ate'='AGITATE'
(Other definitions for agitate that I've seen before include "Disturb or shake" , "Disturb or churn" , "'Stir, excite (7)'" , "Campaign" , "Stir vigorously" .)