Guides for chaps tackling top of Everest (5)
I believe the answer is:
leads
'guides' is the definition.
('lead' can be a synonym of 'guide')
'chaps tackling top of everest' is the wordplay.
'chaps' becomes 'lads' ('lad' can be a synonym of 'chap').
'tackling' indicates putting letters inside (I've seen this in other clues).
'top of' suggests taking the first letters.
The first letter of 'everest' is 'e'.
'lads' placed around 'e' is 'LEADS'.
'for' acts as a link.
(Other definitions for leads that I've seen before include "Goes ahead" , "Actors who play principal roles" , "stars" , "singers principally?" , "Guides; wires" .)