Laid back about S & M? How dreary! (6)
I believe the answer is:
dismal
'dreary' is the definition.
(I know that dreary can be written as dismal)
'laid back about s m?' is the wordplay.
'back' shows that the letters should be reversed in order.
'about' indicates putting letters inside.
'laid' in reverse letter order is 'dial'.
's'+'m'='sm'
'dial' enclosing 'sm' is 'DISMAL'.
'how' is the link.
(Other definitions for dismal that I've seen before include "pitifully bad" , "Very disappointing" , "Showing gloom, dreary" , "Sad and dreary" , "Dull and dreary" .)