Old-timer working only during the day (7)
I believe the answer is:
sundial
'old-timer' is the definition.
(I've seen this before)
'working only during the day' is the wordplay.
I cannot really understand how this works, but
'day' could be 'sun' (abbreviation for Sunday) and 'sun' is located in the answer.
The remaining letters 'dial' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for sundial that I've seen before include "Ancient timepiece" , "Times given by this" , "Shadow timer" , "Natural timekeeper" , "Indicator of time" .)