Old Peruvian picking edges off tiny scab (4)
I believe the answer is:
inca
'old peruvian' is the definition.
(the Inca were a historical people of Peru)
'picking edges off tiny scab' is the wordplay.
'picking edges off' says to take the centre (the edge letters are removed).
'scab' becomes 'ca' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
The centre of 'tiny' is 'in'.
'in'+'ca'='INCA'
Can you help me to learn more?
(Other definitions for inca that I've seen before include "Former emperor" , "Language" , "An old Peruvian like Cain" , "Ancient Peruvian like Cain" , "Pre-conquest South American people" .)