Boringly dull prohibition by health centre (5)
I believe the answer is:
banal
'boringly dull' is the definition.
(I've seen this before)
'prohibition by health centre' is the wordplay.
'prohibition' becomes 'ban' (synonyms).
'by' says to put letters next to each other.
'centre' indicates the central letters.
The middle of 'health' is 'al'.
'ban'+'al'='BANAL'
(Other definitions for banal that I've seen before include "'Hackneyed, trite (5)'" , "Pedestrian" , "Ordinary and uninteresting" , "Lacking originality" , "Obvious and dull" .)