Crossword Genius

I obsess over timepiece, timepiece found in opening of college cupboard (5-7)

Ross

I believe the answer is:

clock-watcher

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'i obsess over timepiece' is the definition.
I can't tell whether this defines the answer.

'timepiece found in opening of college cupboard' is the wordplay.
'timepiece' becomes 'watch' (watch is a kind of timepiece).
'found in' indicates putting letters inside.
'opening of college cupboard' becomes 'clocker' (I can't explain this - if you can you should believe this answer much more).
'watch' going within 'clocker' is 'CLOCK-WATCHER'.

Can you help me to learn more?

(Other definitions for clock-watcher that I've seen before include "Worker too aware of the time" , "One impatient to leave work" , "One who can't wait to stop work" , "Worker preoccupied with finishing time" .)

I've seen this clue in The Times.
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