Earliest of settlers in a mountain range in India, speechless (6)
I believe the answer is:
aghast
'speechless' is the definition.
'earliest of settlers in a mountain range in india' is the wordplay.
'earliest of' suggests taking the first letters.
'in' indicates putting letters inside.
'mountain range in india' becomes 'ghat' (the Western Ghats and Eastern Ghats of India).
The first letter of 'settlers' is 's'.
'a'+'ghat'='aghat'
's' put inside 'aghat' is 'AGHAST'.
(Other definitions for aghast that I've seen before include "Appalled, shocked" , "Filled with consternation or horror" , "Filled with fear or horror" , "Very unhappy" , "Filled with horror or shock" .)