Yell indicating hikers in trouble (6)
I believe the answer is:
shriek
'yell' is the definition.
(shriek is a kind of yell)
'hikers in trouble' is the wordplay.
'in trouble' indicates an anagram.
'hikers' with letters rearranged gives 'SHRIEK'.
'indicating' is the link.
(Other definitions for shriek that I've seen before include "Yell, screech" , "A high-pitched scream" , "Sharp piercing cry" , "Scream or squeal" , "Shrill cry of a shrike" .)