A little tiny piece, you'll admit (3,2)
I believe the answer is:
let in
'admit' is the definition.
(I know that admit can be written as let in)
'a little tiny piece' is the wordplay.
'piece' indicates a hidden word.
'LET IN' is hidden in the letters of 'little tiny'.
'you'll' acts as a link.
This may not be right. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for let in that I've seen before include "Allowed to enter" , "Allow to enter" , "swindle . . ." , "Grant entry" , "Admit" .)