Rotten liar's awful driving (10)
I believe the answer is:
torrential
'driving' is the definition.
(I've seen this before)
'rotten liar's awful' is the wordplay.
'awful' indicates anagramming the letters.
'rotten'+'liar'='rottenliar'
'rottenliar' is an anagram of 'TORRENTIAL'.
(Other definitions for torrential that I've seen before include "Pelting" , "driving" , "(Of rain) very heavy" , "Flowing overwhelmingly" , "(Of rain) falling copiously" .)