Re lung, tobacco is dreadful, almost! (5,3,2,5)
I believe the answer is:
close but no cigar
'almost' is the definition.
(I've seen this in another clue)
're lung tobacco is dreadful' is the wordplay.
'dreadful' indicates an anagram.
're'+'lung'+'tobacco'+'is'='relungtobaccois'
'relungtobaccois' is an anagram of 'CLOSE BUT NO CIGAR'.
(Other definitions for close but no cigar that I've seen before include "It's not quite good enough" , "not good enough for Havana?" , "Very nearly" .)