Bad beer, old pal? Very bad! (10)
I believe the answer is:
deplorable
'very bad' is the definition.
(deplorable means very bad or disgraceful)
'bad beer old pal?' is the wordplay.
'bad' indicates anagramming the letters.
'beer'+'old'+'pal'='beeroldpal'
'beeroldpal' is an anagram of 'DEPLORABLE'.
(Other definitions for deplorable that I've seen before include "Shocking!" , "Atrocious" , "That is to be regretted" .)