Walker, in part, may be a leader of men (5)
I believe the answer is:
tramp
'walker' is the definition.
(street walker)
'in part may be a leader of men' is the wordplay.
'in' means one lot of letters goes inside another.
'may be' is an anagram indicator.
'a leader of' says to take the initial letters.
The first letter of 'men' is 'm'.
'part' with letters rearranged gives 'trap'.
'trap' placed around 'm' is 'TRAMP'.
(Other definitions for tramp that I've seen before include "Vagrant, hobo" , "Derelict - ship" , "Beggar or vagrant" , "Itinerant" , "Footslog" .)