Skinny lad eats midmorning (4)
I believe the answer is:
bony
'skinny' is the definition.
(I've seen this in another clue)
'lad eats midmorning' is the wordplay.
'lad' becomes 'boy' (I've seen this in another clue).
'eats' means one lot of letters goes inside another.
'midmorning' becomes 'n' (I've seen this in other clues).
'boy' going around 'n' is 'BONY'.
(Other definitions for bony that I've seen before include "Scrawny" , "Skeletal" , "Angular" , "[GAUNT] ?" , "Osseous" .)