Eg motel's promise in connection with case (11,4)
I believe the answer is:
portmanteau word
'eg motel's' is the definition.
('motel' is a portmanteau of 'motor' and 'hotel')
'promise in connection with case' is the wordplay.
'promise in connection' becomes 'word' (I can't explain this - if you can you should believe this answer much more).
'with' means one lot of letters go next to another.
'case' becomes 'portmanteau' (portmanteau is a kind of case).
'word' after 'portmanteau' is 'PORTMANTEAU WORD'.
Can you help me to learn more?
(Other definitions for portmanteau word that I've seen before include "Televangelist perhaps" , "E.g. biopic" , "fanzine, for one" , "motel, perhaps" .)