Be quick to appear keen (4,5)
I believe the answer is:
look sharp
'keen' is the definition.
(I've seen this before)
'be quick to appear' is the wordplay.
'be quick' becomes 'sharp' (I've seen this in another clue).
'to' is a charade indicator (letters next to each other) (I've seen this in other clues).
'appear' becomes 'look' (synonyms).
'sharp' after 'look' is 'LOOK SHARP'.
(Other definitions for look sharp that I've seen before include "Be quick!" , "keen" , "Get a move on" , "Get cracking" , "step on it" .)