I miss a lot when drunk or very high (9)
I believe the answer is:
altissimo
'very high' is the definition.
(musical term)
'i miss a lot when drunk' is the wordplay.
'when drunk' indicates an anagram (a drunken or disorderly form of the letters).
'i'+'miss'+'a'+'lot'='imissalot'
'imissalot' anagrammed gives 'ALTISSIMO'.
'or' acts as a link.
(Other definitions for altissimo that I've seen before include "Very highly pitched" , "Very high musical pitch" , "one is almost dizzy" , "Very highly placed" .)