Hikers managed to scream (6)
I believe the answer is:
shriek
'to scream' is the definition.
(shrieking is a kind of screaming)
'hikers managed' is the wordplay.
'managed' is an anagram indicator.
'hikers' with letters rearranged gives 'SHRIEK'.
(Other definitions for shriek that I've seen before include "Scream or squeal" , "Yell, screech" , "A high-pitched shrill cry" , "Sharp piercing cry" , "Hikers (anag.)" .)