A border sign breaking three times now (2,3,6)

'now' is the definition.
(I've seen this in another clue)

'a border sign breaking three times' is the wordplay.
I cannot quite see how this works, but
'a' is found in the answer.
'border' could be 'hem' (I've seen this before) and 'hem' is found in the answer.
'sign' could be 'omen' (omen is a kind of sign) and 'omen' is present in the answer.
'times' could be 'tt' (an abbreviation for time written twice) and 'tt' is located in the answer.
A single letter 't' remains which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?