Solve case for employer with Detective Frost, perhaps, who's exceptionally good? (11)
I believe the answer is:
crackerjack
'exceptionally good?' is the definition.
(I've seen this before)
'solve case for employer with detective frost' is the wordplay.
'solve' becomes 'crack' (I've seen this in another clue).
'case for' suggests removing the centre (the letters which encase the others are used).
'with' is a charade indicator (letters next to each other).
'detective frost' becomes 'jack' (I can't justify this - if you can you should believe this answer much more).
'employer' with its middle taken out is 'er'.
'crack'+'er'+'jack'='CRACKERJACK'
'perhaps who's' is the link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for crackerjack that I've seen before include "Exceptional (thing or person) - 1970s' children's programme" , "Wonderful (person or thing)" , "Exceptionally good" , "Excellent (person or thing)" .)