You're not the only one to go to Chelsea? (4,3,4)
I believe the answer is:
join the club
'you're not the only' is the definition.
I know nothing about this answer so I cannot tell whether it can be defined by this definition.
'one to go to chelsea?' is the wordplay.
I cannot quite see how this works, but
'one' could be 'club' (I've seen this before) and 'club' is found in the answer.
'go' could be 'joint' (jointing is a kind of going) and 'joint' is present in the answer.
The remaining letters 'he' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for join the club that I've seen before include "Welcome" , "We're both in that difficult situation!" , "What you do if you sign for United" , "Things are just as bad for me!" , "Girl's pregnant" .)