It justifies a fling in the field of sport (7)
I believe the answer is:
javelin
'field of sport' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe there's a link between them I don't understand?
'it justifies a fling in' is the wordplay.
I cannot quite understand how this works, but
'it' could be 'e' ('e' can mean 'electronic' which is similar to 'IT') and 'e' is found in the answer.
'a' is found in the answer.
'in' is within the answer.
This may be the basis of the clue (or it may be nonsense).
'the' is the link.
Can you help me to learn more?
(Other definitions for javelin that I've seen before include "Sporting missile" , "Spear for field event" , "Long spear" , "Type of spear" , "Field event missile" .)