Bit of grass scouts lost on summit of Kilimanjaro (7)
I believe the answer is:
tussock
'bit of grass' is the definition.
'scouts lost on summit of kilimanjaro' is the wordplay.
'lost' is an anagram indicator.
'on' says to put letters next to each other.
'summit of' says to take the initial letters.
The initial letter of 'kilimanjaro' is 'k'.
'scouts' is an anagram of 'tussoc'.
'tussoc'+'k'='TUSSOCK'
(Other definitions for tussock that I've seen before include "Grassy clump" , "mound" , "Dense clump of grass - stuck so (anag)" , "Clump of hair" , "hump" .)