Notorious logical figure having change of heart? Just a bit (5)
I believe the answer is:
speck
'a bit' is the definition.
(I've seen this before)
'notorious logical figure having change of heart?' is the wordplay.
'notorious logical figure' becomes 'spek' (I can't justify this - if you can you should give a lot more credence to this answer).
'having' means one lot of letters goes inside another.
'change' becomes 'ace' (ace is a kind of change).
'of heart?' says to take the centre (I've seen 'heart' mean this).
The middle of 'ace' is 'c'.
'spek' going around 'c' is 'SPECK'.
'just' acts as a link.
Can you help me to learn more?
(Other definitions for speck that I've seen before include "Bit of dust" , "Dot" , "Italian ham" , "lot of fat in school?" , "Tiny spot" .)