Commonplace boycott on an inexperienced driver (5)
I believe the answer is:
banal
'commonplace' is the definition.
(I know that commonplace can be written as banal)
'boycott on an inexperienced driver' is the wordplay.
'boycott' becomes 'ban' (I've seen this in another clue).
'on' means one lot of letters go next to another.
'an' becomes 'a'.
'inexperienced driver' becomes 'l' (a learner driver's car carries L-plates).
'ban'+'a'+'l'='BANAL'
(Other definitions for banal that I've seen before include "Obvious and boring" , "Trite or fatuous" , "Old hat" , "Ordinary and uninteresting" , "Tediously unoriginal" .)