Motivation of troublemaker at university, a London one (7)

I believe the answer is:

impulse

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'motivation' is the definition.
(I know that impulse is a type of motivation)

'troublemaker at university a london one' is the wordplay.
'troublemaker' becomes 'imp' (little devil).
'at' means one lot of letters go next to another.
'university' becomes 'U' (abbreviation for university).
'a london one' becomes 'lse' (I am not sure about this - if you are sure you should believe this answer much more).
'imp'+'u'+'lse'='IMPULSE'

'of' acts as a link.

Can you help me to learn more?

(Other definitions for impulse that I've seen before include "Sudden or instinctive desire" , "Sudden urge to act" , "Miles up (anag)" , "A sudden urge or whim" , "A push; whim" .)

I've seen this clue in The Guardian.

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