Mud's picked up on eastern walk (6)
I believe the answer is:
stride
'walk' is the definition.
(stride can mean to walk around)
'mud's picked up on eastern' is the wordplay.
'mud's' becomes 'dirt's'.
'picked up' shows that the letters should be reversed in order.
'on' says to put letters next to each other.
'eastern' becomes 'e'.
'dirts' back-to-front is 'strid'.
'strid'+'e'='STRIDE'
(Other definitions for stride that I've seen before include "style of jazz piano" , "jazz piano-playing" , "Long pace" , "Move with long steps" , "Step out energetically" .)