Having entered the Indy 500, European is exhausted (4)
I believe the answer is:
used
'is exhausted' is the definition.
(I've seen this in another clue)
'having entered the indy 500 european' is the wordplay.
I cannot really understand how this works, but
'500' could be 'd' (Roman numeral for 500) and 'd' is present in the answer.
'european' could be 'e' (abbreviation e.g. EU) and 'e' is located in the answer.
The remaining letters 'us' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for used that I've seen before include "Hand-me-down" , "took a chance on becoming dependent" , "Was treating" , "Second-hand, not new" , "Employed - exploited" .)