Nasty puncture — it's been mended touring Alaska (9)
I believe the answer is:
snakebite
'nasty puncture' is the definition.
(wound made by a snake)
'it's been mended touring alaska' is the wordplay.
'mended' indicates anagramming the letters.
'touring' means one lot of letters goes inside another (touring can mean going round).
'alaska' becomes 'AK' (abbreviation).
'its'+'been'='itsbeen'
'itsbeen' with letters rearranged gives 'snebite'.
'snebite' placed around 'ak' is 'SNAKEBITE'.
(Other definitions for snakebite that I've seen before include "It might kill you" , "A venomous concoction" , "Cider-lager drink" , "That could be fatal!" , "Cider mixed with lager" .)