Decorate rear of cab in some backward society (6)
I believe the answer is:
emboss
'decorate' is the definition.
(I've seen this in another clue)
'rear of cab in some backward society' is the wordplay.
'rear of' suggests the final letters.
'in' is an insertion indicator.
'backward' says the letters should be written backwards.
'society' becomes 's' (common abbreviation in names of organisations).
The final letter of 'cab' is 'b'.
'b' placed inside 'some' is 'sobme'.
'sobme' backwards is 'embos'.
'embos'+'s'='EMBOSS'
(Other definitions for emboss that I've seen before include "opposite of grave" , "Raise (a design) in relief" , "Provide relief" , "Ornament with slightly raised pattern" , "Impress" .)