Boffin's formula for e? (7)
I believe the answer is:
egghead
'boffin's' is the definition.
(I've seen this before)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for egghead that I've seen before include "Brainy type" , "Very academic person" , "An intellectual (inf.)" , "Boffin" , "brain" .)