That's my lot, eaten by swimmer of evil intent (8)
I believe the answer is:
fiendish
'swimmer of evil intent' is the definition.
Both the definition and answer are adjectives. Maybe they are linked in a way I don't understand?
'that's my lot eaten' is the wordplay.
I cannot quite see how this works, but
'that's' could be 'ie' and 'ie' is present in the answer.
'lot' could be 'd' and 'd' is found within the answer.
This explanation may well be incorrect...
'by' acts as a link.
Can you help me to learn more?
(Other definitions for fiendish that I've seen before include "Terrible" , "Finished (anag) - demonic" , "Extremely cruel" , "how diabolically cruel" , "like some Sudokus" .)