Extract as much as possible from, at heart, timid sort (4)
I believe the answer is:
milk
'extract as much as possible' is the definition.
'milk' can be an answer for 'extract' (milking is a kind of extracting). I'm unsure of the 'as much as possible' bit.
'at heart timid sort' is the wordplay.
'at heart' says to take the centre.
'sort' becomes 'ilk' (ilk can mean a type or kind).
The middle letter of 'timid' is 'm'.
'm'+'ilk'='MILK'
'from' acts as a link.
Can you help me to learn more?
(Other definitions for milk that I've seen before include "White liquid" , "Exploit" , "Source of cream/butter" , "Extract money from" , "A white drink" .)