Dull finish, following insufficiency (10)
I believe the answer is:
lacklustre
'dull' is the definition.
(similar in meaning)
'finish following insufficiency' is the wordplay.
'finish' becomes 'lustre' (lustre is a kind of finish).
'following' is a charade indicator (letters next to each other).
'insufficiency' becomes 'lack' (I've seen this in another clue).
'lustre' after 'lack' is 'LACKLUSTRE'.
(Other definitions for lacklustre that I've seen before include "Dull; boring" , "sluggish performance" , "Prosaic" , "Without vitality" , "Unimaginative" .)