Jim pronounced expert, though actually very bad (8)
I believe the answer is:
gimcrack
'actually very bad' is the definition.
Both the definition and answer are adjectives. Perhaps you can see a link between them that I don't see?
'jim pronounced expert' is the wordplay.
I cannot quite see how this works, but
'expert' could be 'crack' (as in 'a crack team') and 'crack' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
'though' is the link.
Can you help me to learn more?
(Other definitions for gimcrack that I've seen before include "Cheap and unreliable" , "Cheap and shoddy" , "Of ornament, showy but worthless" , "Shoddy; a poorly made article" , "Tinpot" .)