Walks for miles - into ambushes! (6)
I believe the answer is:
tramps
'walks' is the definition.
(tramp is a kind of walk)
'miles into ambushes' is the wordplay.
'miles' becomes 'm' (common abbreviation).
'into' means one lot of letters goes inside another.
'ambushes' becomes 'traps' ('trap' can be a synonym of 'ambush').
'm' placed within 'traps' is 'TRAMPS'.
'for' is the link.
(Other definitions for tramps that I've seen before include "Walks with heavy footfall" , "Walks heavily like hobos" , "Walks heavily with vagrants" , "Become hard or solid" , "Walks heavily like hoboes" .)