Train A&E nurse to bind together (8)

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

'train ae nurse' is the wordplay.
I cannot really see how this works, but
'train' could be 'string' (synonyms) and 'string' is located in the answer.
'ae' is found in the answer.
This accounts for all the letters.
This explanation may well be incorrect...

'to' is the link.

Can you help me to learn more?