On the contrary, feels freer acknowledging this has overshadowed their life's work (6)
I believe the answer is:
career
'life's work' is the definition.
(someone's work or profession)
'on the contrary feels freer acknowledging this has' is the wordplay.
'on the contrary' shows that the letters should be reversed in order (letters in the opposite or contrary direction).
'this has' says the answer is hidden in the clue.
'reerac' is hidden in the letters of 'feels freer acknowledging'.
'reerac' written backwards gives 'CAREER'.
'overshadowed their' is the link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for career that I've seen before include "'Occupation, profession (6)'" , "job, but one that lasts for years?" , "History of working life (6)" , "Lifetime occupation" , "Vocation; rush" .)