Gathered action involves French duke (7)
I believe the answer is:
deduced
'gathered' is the definition.
(I've seen this in another clue)
'action involves french duke' is the wordplay.
'action' becomes 'deed' (deed is a kind of action).
'involves' means one lot of letters goes inside another.
'french duke' becomes 'duc' ('duke' in French).
'deed' going around 'duc' is 'DEDUCED'.
(Other definitions for deduced that I've seen before include "Gathered" , "Concluded" , "Arrived at by reasoning" , "Inferred" , "Came to logical conclusion like Sherlock" .)