Bit of grass scouts lost on summit of Kilimanjaro (7)
I believe the answer is:
Here is my best explanation:
'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'.
(Other definitions for tussock that I've seen before include "Grass clump", "Grassy clump", "Clump of hair", "Dense clump of grass - stuck so (anag)", "Thick patch of grass", "hump", "(Of grass) cut", "Clump of grass", "Tuft of grass" and "Bushy clump of grass".)