Horse carrying daughter and old man up — one of two runners? (4,3)
I believe the answer is:
cold tap
'one of two runners?' is the definition.
(tap with running water, along with the hot tap)
'horse carrying daughter and old man up' is the wordplay.
I cannot quite see how this works, but
'daughter' could be 'd' (genealogical abbreviation) and 'd' is present in the answer.
'horse' could be 'colt' (I've seen this before) and 'colt' is located in the leftover letters.
'man' could be 'p' (abbreviation for pawn, a chess piece or 'man') and 'p' is found in the answer.
A single letter 'a' remains which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
(Another definition for cold tap that I've seen is " It is often marked blue".)