He's coming down - for the day! (7)
I believe the answer is:
tripper
'he's coming down for the day' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'he's' is the wordplay.
I cannot really understand how this works, but
'he' could be 'tripp' and 'tripp' is located in the answer.
The remaining letters 'er' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for tripper that I've seen before include "One who makes an excursion" , "Tourist" , "One hoping to enjoy journey" , "person having highly enjoyable experience?" , "at risk of sustaining injury?" .)