Run into pack round walk (5)
I believe the answer is:
tramp
'walk' is the definition.
(I know that tramp is a type of walk)
'run into pack round' is the wordplay.
'run into' becomes 'r' (I've seen this in other clues).
'pack' becomes 'tamp' (synonyms).
'round' means one lot of letters goes inside another.
'r' going within 'tamp' is 'TRAMP'.
(Other definitions for tramp that I've seen before include "Go heavily" , "March heavily like hobo" , "Attack with knife" , "Heavily plod around" , "Walk heavily - steamer" .)