Smear evenly about and back (4)
I believe the answer is:
daub
'smear' is the definition.
(I know that smear can be written as daub)
'evenly about and back' is the wordplay.
'evenly' means one should take alternating letters (the letters in even-numbered positions).
'back' says the letters should be written backwards.
'about'+'and'='aboutand'
The alternate letters of 'aboutand' are 'buad'.
'buad' in reverse letter order is 'DAUB'.
(Other definitions for daub that I've seen before include "Smear; bad painting" , "Crude painting" , "Do graffiti" , "Smear; plaster" , "Smear carelessly" .)