Single out the cold water pipe with the hole in it (6)
I believe the answer is:
Here is my best explanation:
'single out' is the definition.
'the cold water pipe with the hole in it' is the wordplay.
'the cold' becomes 'c' (eg on taps).
'water pipe' becomes 'hose' (I've seen this before).
'with' is a charade indicator (letters next to each other).
'the hole' becomes 'o'.
'in it' is an insertion indicator.
'chose' placed around 'o' is 'CHOOSE'.
(Other definitions for choose that I've seen before include "Elect", "Select, pick", "Pick, select.", "So echo (anag) - wish", "Vote", "Make a selection", "Select, opt for", "Opt" and "Think fit".)