Prohibition on nearly everything thats commonplace (5)
I believe the answer is:
banal
'commonplace' is the definition.
('banal' can be a synonym of 'commonplace')
'prohibition on nearly everything' is the wordplay.
'prohibition' becomes 'ban' (ban is a kind of prohibition).
'on' is a charade indicator (letters next to each other).
'nearly' means to remove the last letter.
'everything' becomes 'all' (I've seen this before).
'all' with its last letter taken away is 'al'.
'ban'+'al'='BANAL'
'thats' is the link.
(Other definitions for banal that I've seen before include "Obvious and boring" , "Trite or fatuous" , "Uninspiring" , "Tediously commonplace" , "Lacking originality" .)