Incompetent fellow trapped in kitchen cupboard? (5)
I believe the answer is:
unfit
'incompetent' is the definition.
(I've seen this in another clue)
'fellow trapped in kitchen cupboard?' is the wordplay.
'fellow' becomes 'F' (abbreviation - of a society etc.).
'trapped in' is an insertion indicator.
'kitchen cupboard?' becomes 'unit' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'f' inserted within 'unit' is 'UNFIT'.
Can you help me to learn more?
(Other definitions for unfit that I've seen before include "Not in good physical shape (5)" , "Unsuitable" , "Ill-equipped" , "Ill - out of shape" , "In bad physical condition" .)