Resolve of French repeatedly to capture Channel Islands (6)
I believe the answer is:
decide
'resolve' is the definition.
(I know that resolve can be written as decide)
'of french repeatedly to capture channel islands' is the wordplay.
'of french' becomes 'de' ('of' in French).
'repeatedly' shows that letters should be duplicated.
'to capture' means one lot of letters goes inside another.
'channel islands' becomes 'CI'.
'de' duplicated is 'dede'.
'dede' going around 'ci' is 'DECIDE'.
(Other definitions for decide that I've seen before include "Resolve, settle (issue)" , "Choose" , "Adjudicate" , "Reach a judgment" , "Resolve; give judgement" .)