Chap stopping fool in afternoon meal getting some water (6,3)
I believe the answer is:
tasman sea
'some water' is the definition.
(I've seen this before)
'chap stopping fool in afternoon meal' is the wordplay.
'chap' becomes 'man' (chap can mean a man).
'stopping' means one lot of letters goes inside another (stopping can mean blocking a gap).
'fool' becomes 'ass' (both can mean a stupid person).
'in' indicates putting letters inside.
'afternoon meal' becomes 'tea' (meal eaten in the afternoon).
'man' put into 'ass' is 'asmans'.
'asmans' going into 'tea' is 'TASMAN SEA'.
'getting' acts as a link.
(Other definitions for tasman sea that I've seen before include "it's wet" , "Cook explored here" , "stretch of water" , "Ocean area between Australia and New Zealand" , "Body of water separating Australia and New Zealand" .)