Remains on United's boring team (7)
I believe the answer is:
residue
'remains' is the definition.
(thesaurus)
'united's boring team' is the wordplay.
'united' becomes 'u'.
'boring' indicates putting letters inside (some letters must 'bore' a hole into other letters).
'team' becomes 'reside' (I can't justify this - if you can you should believe this answer much more).
'u' inserted inside 'reside' is 'RESIDUE'.
'on' is the link.
Can you help me to learn more?
(Other definitions for residue that I've seen before include "Deposit" , "Material left" , "Small amount remaining" , "Remaining portion" , "Net worth of estate" .)