Rub out two consecutive letters at the front (6)
I believe the answer is:
efface
'rub out' is the definition.
(synonyms)
'two consecutive letters at the front' is the wordplay.
'two consecutive letters at' becomes 'ef' (I can't explain this - if you can you should give a lot more credence to this answer).
'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" .)