Good French tenor's headgear (6)
I believe the answer is:
bonnet
'headgear' is the definition.
(bonnet is a kind of headgear)
'good french tenor's' is the wordplay.
'good french' becomes 'bonne'.
'tenor' becomes 't'.
'bonne'+'t'='BONNET'
(Other definitions for bonnet that I've seen before include "Car part" , "Lady's old-fashioned hat" , "Lady's hat musically associated with Easter" , "Over; mentioned earlier" , "Woman's hat associated with Easter" .)