Glide over snow jolly hard, joining Iceland battle (8)
I believe the answer is:
skirmish
'battle' is the definition.
(I know that skirmish is a type of battle)
'glide over snow jolly hard joining iceland' is the wordplay.
'glide over snow' becomes 'ski' (I've seen this before).
'jolly' becomes 'RM' (jolly can mean a Royal Marine).
'hard' becomes 'h' (abbreviation used in pencil classifications).
'joining' means one lot of letters go next to another.
'iceland' becomes 'is'.
'h' after 'is' is 'ish'.
'ski'+'rm'+'ish'='SKIRMISH'
(Other definitions for skirmish that I've seen before include "Brief military engagement" , "Minor fight or conflict" , "'Brief, minor fight (8)'" , "Scrap" , "Minor short-term fight" .)