Boffin for example, good man, a mastermind ultimately (7)
I believe the answer is:
egghead
'boffin' is the definition.
(I've seen this before)
'example good man a mastermind ultimately' is the wordplay.
'example' becomes 'eg'.
'good' becomes 'g' (abbreviation).
'man' becomes 'he' (**).
'ultimately' suggests the final letters.
The final letter of 'mastermind' is 'd'.
'eg'+'g'+'he'+'a'+'d'='EGGHEAD'
'for' acts as a link.
(Other definitions for egghead that I've seen before include "Boffin" , "Intellectual person" , "Brainiac" , "Cracked" , "Intellectual, studious academic" .)