The one that didn't get on with you (4)
I believe the answer is:
thee
'you' is the definition.
(I've seen this before)
'the one that didn't get on' is the wordplay.
I cannot quite see how this works, but
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is present in the answer.
The remaining letters 'hee' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'with' is the link.
Can you help me to learn more?
(Other definitions for thee that I've seen before include "Quaker 'you'" , "Archaic form of 'you'" , "Poetically you" , "You in the olden days" , "You (arch.)" .)