Cruel individual is miserable first (6)
I believe the answer is:
sadist
'cruel individual' is the definition.
'sadist' can be an answer for 'individual' (sadist is a kind of individual). I am unsure of the 'cruel' bit.
'miserable first' is the wordplay.
'miserable' becomes 'sad' (similar in meaning).
'first' becomes 'ist' (ist resembles 1st).
'sad'+'ist'='SADIST'
'is' acts as a link.
Can you help me to learn more?
(Other definitions for sadist that I've seen before include "One gets pleasure from inflicting pain on others" , "Savage'!?" , "Cruel person, takes pleasure in it" , "One who enjoys cruelty" , "It's sad to find person who enjoys hurting others" .)