Be behind redhead in shadow (5)
I believe the answer is:
trail
'shadow' is the definition.
(trailing is a kind of shadowing)
'be behind redhead in' is the wordplay.
'be behind' becomes 'tail' (I've seen this in another clue).
'redhead' becomes 'r' (the head letter of red).
'in' indicates putting letters inside.
'tail' placed around 'r' is 'TRAIL'.
(Other definitions for trail that I've seen before include "Beaten path through the countryside" , "Rough track blazed through wild or hilly country" , "Linger behind" , "Scent or track followed in hunting" , "Dog - track" .)