Rub out two consecutive letters at the front (6)
I believe the answer is:
efface
'rub out' is the definition.
(I know that rub out can be written as efface)
'two consecutive letters at the front' is the wordplay.
'two consecutive letters at' becomes 'ef' (I am not sure about this - if you are sure you should believe this answer much more).
'the front' becomes 'face' (face is a kind of front).
'ef'+'face'='EFFACE'
Can you help me to learn more?
(Other definitions for efface that I've seen before include "Remove all trace of" , "Erase a mark from a surface" , "The selling of goods in large quantities" , "Do away with" , "Obliterate by rubbing out" .)