Tie it with it (12)
I believe the answer is:
relationship
'it' is the definition.
The definition suggests a singular noun which matches the answer.
'tie it' is the wordplay.
'tie' becomes 'relation' (I've seen this in another clue).
'it' becomes 'ship' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'relation'+'ship'='RELATIONSHIP'
'with' acts as a link.
Can you help me to learn more?
(Other definitions for relationship that I've seen before include "Emotional bond" , "Romance" , "Emotional association between two people" , "Family connection" , "Linkage; affair" .)