A president, remarkably banal (10)
I believe the answer is:
pedestrian
'banal' is the definition.
(thesaurus)
'a president remarkably' is the wordplay.
'remarkably' indicates anagramming the letters.
'a'+'president'='apresident'
'apresident' anagrammed gives 'PEDESTRIAN'.
(Other definitions for pedestrian that I've seen before include "Walker; prosaic" , "flat" , "not very fast" , "Unexciting" , "wearer of leather?" .)