Heartless raiders panicking in range (6)
I believe the answer is:
sierra
'range' is the definition.
(sierra is a kind of range)
'heartless raiders panicking' is the wordplay.
'heartless' says to hollow out the word (remove centre letters).
'panicking' indicates anagramming the letters.
'raiders' with its centre taken out is 'raiers'.
'raiers' is an anagram of 'SIERRA'.
'in' acts as a link.
(Other definitions for sierra that I've seen before include "Spanish range of mountains" , "A Spanish mountain chain (6)" , "mountain area" , "Long range" , "Mountain range -- code word for S" .)