Put two and two together again - and mend! (6)
I believe the answer is:
repair
'mend' is the definition.
(I know that mend can be written as repair)
'put two and two together again' is the wordplay.
I cannot quite see how this works, but
'two' could be 'pair' (pair is a kind of two) and 'pair' is found within the answer.
'again' could be 're' (prefix meaning 'again') and 're' is found in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
'and' is the link.
Can you help me to learn more?
(Other definitions for repair that I've seen before include "Restore; go" , "Correct" , "Mend - go" , "Mend, put right" , "Restore to good order" .)