When connected, odd bits may drop off (4)
I believe the answer is:
once
'when' is the definition.
(synonyms)
'connected odd bits may drop off' is the wordplay.
I cannot really see how this works, but
'connected' could be 'on' (synonyms) and 'on' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for once that I've seen before include "Sometime" , "One-time musical film and song" , "Some time back" , "On one occasion" , "In days gone by" .)