Piece of eight in your pocket (4)
I believe the answer is:
tiny
'pocket' is the definition.
(I've seen this before)
'piece of eight in your' is the wordplay.
'piece of' says the answer is hidden in the clue.
'TINY' is hidden within 'eight in your'.
(Other definitions for tiny that I've seen before include "with sharp points?" , "Extremely small" , "Little" , "Wee" , "Minuscule" .)