I obsess over timepiece, timepiece found in opening of college cupboard (5-7)
I believe the answer is:
clock-watcher
'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" .)