Climbing mountains with peaks of snow hurts a little (6)
I believe the answer is:
splash
'a little' is the definition.
(a splash of something is a little of it)
'climbing mountains with peaks of snow hurts' is the wordplay.
'climbing' shows that the letters should be reversed in order (in a down clue, letters climb up).
'mountains' becomes 'alps' (European mountain range).
'with' is a charade indicator (letters next to each other).
'peaks of' suggests taking the first letters (the top letters are the peaks of the words).
The initial letters of 'snow hurts' is 'sh'.
'alps' back-to-front is 'spla'.
'spla'+'sh'='SPLASH'
(Other definitions for splash that I've seen before include "Effect of hitting water (or headlines!)" , "Bright patch of colour; fall in drops" , "Lead news story" , "Fall in irregular drops" , "Drop" .)