I tend not to mind knocking off early at work, not at all (4,7,2)
I believe the answer is:
dont mention it
'not at all' is the definition.
(I've seen this before)
'i tend not to mind knocking off early at work' is the wordplay.
I cannot really understand how this works, but
'i' could be 'me' and 'me' is present in the answer.
an anagram of 'not' is 'ont' which is within the answer.
'at' could be 'on' (location) and 'on' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for dont mention it that I've seen before include "no problem!" , "That's all right" , "keep it secret" , "Refrain from talking about the situation" , "My pleasure!" .)