Veronica went very fast, stuck with ultimately large fine (9)
I believe the answer is:
speedwell
'veronica' is the definition.
(speedwell can mean a veronica plant)
'with ultimately large fine' is the wordplay.
'with' means one lot of letters go next to another.
'ultimately large' becomes 'speed' (I am not sure about this - if you are sure you should believe this answer much more).
'fine' becomes 'well' (similar in meaning).
'speed'+'well' is 'SPEEDWELL'.
'went very fast stuck' is the link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for speedwell that I've seen before include "Small creeping herbaceous plant with blue or pink flowers" , "Small plant, veronica" , "Small blue flower of the genus veronica" , "bloomer?" , "Flowering plant" .)