Celtic cup upset inspiring lines like this (7,4)
I believe the answer is:
cryptic clue
'celtic cup upset inspiring lines' is the definition.
I don't know anything about this answer so I cannot judge whether this works.
'like this' is the wordplay.
'like' becomes 'cryptic' (I can't explain this - if you can you should give a lot more credence to this answer).
'this' becomes 'clue' (the clue referring to itself!).
'cryptic'+'clue'='CRYPTIC CLUE'
Can you help me to learn more?
(Another definition for cryptic clue that I've seen is " Hint more mysterious than this one!".)