Case full of French wine mostly, but no great shakes (7)
I believe the answer is:
trivial
'no great shakes' is the definition.
(thesaurus)
'case full of french wine mostly' is the wordplay.
'case' becomes 'trial' (I've seen this in other clues**).
'full of' is an insertion indicator.
'french wine' becomes 'vin' (I've seen this before).
'mostly' means to remove the last letter.
'vin' with its last letter taken away is 'vi'.
'trial' going around 'vi' is 'TRIVIAL'.
'but' acts as a link.
(Other definitions for trivial that I've seen before include "Of little importance" , "Meaningless" , "lacking weight" , "Petty, piffling" , "Banal" .)