Last couple in invite covered by ‘plus one’ possibly? More than sufficient (9)
I believe the answer is:
plenteous
'sufficient' is the definition.
(thesaurus)
'last couple in invite covered by plus' is the wordplay.
'last' suggests the final letters.
'in' is an insertion indicator.
'invite' becomes 'ento' (I can't justify this - if you can you should give a lot more credence to this answer).
'covered by' is an insertion indicator.
The final letter of 'couple' is 'e'.
'e' put inside 'ento' is 'enteo'.
'enteo' put inside 'plus' is 'PLENTEOUS'.
'one possibly? more than' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for plenteous that I've seen before include "Well-provided" , "Abundant" .)