Acceptable number still regularly used vessel (7)
I believe the answer is:
utensil
'vessel' is the definition.
(thesaurus)
'acceptable number still regularly' is the wordplay.
'acceptable' becomes 'u' ((Film classification)).
'number' becomes 'ten' (ten is a kind of number).
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
The alternating letters of 'still' are 'sil'.
'u'+'ten'+'sil'='UTENSIL'
'used' is the link.
(Other definitions for utensil that I've seen before include "Gadget" , "knife, maybe" , "Item, eg for kitchen" , "Can opener, for example" , "Tool for practical use" .)