European ringleader getting rodent with hesitation? That's a mistake (7)
I believe the answer is:
erratum
'that's a mistake' is the definition.
(erratum is a kind of mistake)
'european ringleader getting rodent with hesitation?' is the wordplay.
'european ringleader' becomes 'er' (this could be a standard abbreviation I've not previously seen).
'getting' says to put letters next to each other.
'rodent' becomes 'rat' (rat is a kind of rodent).
'with' is a charade indicator (letters next to each other).
'hesitation?' becomes 'um' (um is said in hesitation).
'er'+'rat'+'um'='ERRATUM'
Can you help me to learn more?
(Other definitions for erratum that I've seen before include "fluff on paper" , "Faux pas" , "Typo" , "Mistake in printed work" , "gaffe" .)