Here, time's up! (5,5)
I believe the answer is:
clock tower
'here' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.
'time's up' is the wordplay.
I cannot really understand how this works, but
'time' could be 'clock' (synonyms) and 'clock' is found in the answer.
The remaining letters 'tower' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for clock tower that I've seen before include "one looked up to for a time?" , "will it hold up the enemy's progress?" , "Big Ben, for example" .)