Debutant essentially keeping fans excited in French Open (8)
I believe the answer is:
unfasten
'open' is the definition.
(unfastening is a kind of opening)
'debutant essentially keeping fans excited in french' is the wordplay.
'essentially' means to look at the middle letters.
'keeping' indicates putting letters inside.
'excited' is an anagram indicator.
'in french' becomes 'en' ('en' can be French for 'in' e.g. en France).
The centre of 'debutant' is 'ut'.
'fans' is an anagram of 'nfas'.
'ut' placed around 'nfas' is 'unfast'.
'unfast'+'en'='UNFASTEN'
(Other definitions for unfasten that I've seen before include "Undo" , "Loosen or open, say seatbelt" , "Let go" , "Unlock" , "tie? No" .)