Plea from someone wet and helpless with a certain peck? (3,7)
I believe the answer is:
dry measure
'peck?' is the definition.
(peck is a kind of dry measure)
I can't explain the remainder of the clue.
(Other definitions for dry measure that I've seen before include "unit of size" , "Law against drinking" , "unit of quantity for corn etc." , "pint, for example" , "It shows capacity" .)