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' says to take the centre.
The centre 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" .)