Single out the cold water pipe with the hole in it (6)
I believe the answer is:
choose
'single out' is the definition.
(I've seen this in another clue)
'cold water pipe with the hole in it' is the wordplay.
'cold water' becomes 'C' (symbol for the cold tap).
'pipe' becomes 'hose' (I've seen this before).
'with' says to put letters next to each other.
'the hole' becomes 'O'.
'in it' means one lot of letters goes inside another.
'c'+'hose'='chose'
'chose' placed around 'o' is 'CHOOSE'.
'the' is the link.
(Other definitions for choose that I've seen before include "Make a selection" , "Elect" , "Vote" , "So echo (anag) - wish" , "Select, opt for" .)