Idiot follows bullock with ponytail - it's ironic! (8)
I believe the answer is:
oxymoron
'ponytail it's ironic' is the definition.
I can't judge whether this defines the answer.
'idiot follows bullock' is the wordplay.
'idiot' becomes 'moron' (synonyms).
'follows' is a charade indicator (letters next to each other).
'bullock' becomes 'oxy' (I am not sure about this - if you are sure you should believe this answer much more).
'moron' after 'oxy' is 'OXYMORON'.
'with' acts as a link.
Can you help me to learn more?
(Other definitions for oxymoron that I've seen before include "Phrase or sentence with inherent contradiction" , "Sentence that appears to contradict itself" , "Paradoxical figure of speech" , "'Figure of speech, it contains contradictory terms (8)'" , "Figure of speech using contradictory terms" .)