Furnishes egghead with sarcastic remarks (6)
I believe the answer is:
equips
'furnishes' is the definition.
(equipping is a kind of furnishing)
'egghead with sarcastic remarks' is the wordplay.
'egghead' becomes 'e' (head letter of 'egg').
'with' says to put letters next to each other.
'sarcastic remarks' becomes 'quips' (quip is a kind of remark. I am not sure about the 'sarcastic' bit.).
'e'+'quips'='EQUIPS'
Can you help me to learn more?
(Other definitions for equips that I've seen before include "Supplies" , "Provides with the necessary tools" .)