Had I not gone off by myself punctually (2,4)
I believe the answer is:
on time
'punctually' is the definition.
Both the answer and definition are adverbs. Maybe you can see an association between them that I don't see?
'had i not gone off by myself' is the wordplay.
I cannot quite understand how this works, but
'i' could be 'me' and 'me' is located in the answer.
an anagram of 'not' is 'ont' which is present in the answer.
'myself' could be 'i' and 'i' is found within the answer.
This accounts for all the letters.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for on time that I've seen before include "Arriving when due" , "Punctual, not late" , "Not running late" , "according to schedule" , "as expected" .)