Misgiving about extremely large jacket (7)
I believe the answer is:
doublet
'jacket' is the definition.
(doublet is a kind of jacket)
'misgiving about extremely large' is the wordplay.
'misgiving' becomes 'doubt' (I've seen this before).
'about' indicates putting letters inside.
'extremely large' becomes 'le' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'doubt' placed around 'le' is 'DOUBLET'.
Can you help me to learn more?
(Other definitions for doublet that I've seen before include "Elizabethan man's jacket (worn with hose)" , "Jacket once, went with hose" , "Pair of similar things" , "Pairing" , "Formerly, a man's close-fitting jacket" .)