Tied up - and about to tie the knot (7)
I believe the answer is:
engaged
'tied up' is the definition.
('engaged' can be a synonym of 'tied up')
'and about to tie the knot' is the wordplay.
I cannot really see how this works, but
'and' could be 'n' (common abbreviation for 'and') and 'n' is located in the answer.
'about' could be 'a' (abbreviation in Chambers) and 'a' is present in the answer.
The remaining letters 'egged' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for engaged that I've seen before include "Fully committed - to get married?" , "as a result of a proposal" , "Affianced" , "preparing for the match?" , "Occupied with business - about to marry?" .)