There it is, heartless, backward, the pick of society for the most part and highly strung (8)
I believe the answer is:
volatile
'highly strung' is the definition.
Both the definition and answer are adjectives.
Maybe you can see a link between them that I can't see?
'there it is heartless backward the pick of society for the most part' is the wordplay.
I cannot really understand how this works, but
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is found within the answer.
'of' could be 'o' and 'o' is found within the answer.
'part' could be 'la' (la is a kind of part) and 'la' is found within the answer.
The remaining letters 'vile' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'and' is the link.
Can you help me to learn more?
(Other definitions for volatile that I've seen before include "A live lot being changeable" , "Easily evaporated" , "A love lit badly could be changeable" , "apt to change" , "Liable to sudden change, erratic" .)