Love, then break up? It's likely to be an illusion (2,3)
I believe the answer is:
op art
'be an illusion' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'love then break up? it's likely' is the wordplay.
I cannot quite see how this works, but
'love' could be 'o' (love means zero in tennis) and 'o' is found in the answer.
'break' could be 'part' and 'part' is present in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
'to' is the link.
Can you help me to learn more?
(Other definitions for op art that I've seen before include "abstract works at Tate Modern?" , "1960s' style of abstract painting, with dramatic visual effects" , "modern movement" , "Illusory form of painting" , "Nineteen sixties illusory painting style" .)