Wet some tin accidentally (7)
I believe the answer is:
moisten
'wet' is the definition.
(moistening is a kind of wetting)
'some tin accidentally' is the wordplay.
'accidentally' indicates an anagram (a chaotic or accidental ordering of the letters).
'some'+'tin'='sometin'
'sometin' with letters rearranged gives 'MOISTEN'.
(Other definitions for moisten that I've seen before include "contrary to sixteen down [DEHYDRATE]!" , "water a bit" , "Add water - dampen" , "What one's eyes may do!" , "It's on me (anag)" .)