Skipper clambered inside (4)
I believe the answer is:
lamb
'skipper' is the definition.
(I've seen this before)
'clambered inside' is the wordplay.
'inside' says the answer is hidden in the clue.
'LAMB' is hidden in the letters of 'clambered'.
(Other definitions for lamb that I've seen before include "Tender sheep meat" , "author?" , "Skipper" , "essayists?" , "Charles ---, essayist; meek animal" .)