Crossword Genius

Exhausted American editor on horseback (4,2)

Ross

I believe the answer is:

used up

'exhausted' is the definition.
('used-up' can be similar in meaning to 'exhausted')

'american editor on horseback' is the wordplay.
'american' becomes 'us'.
'editor' becomes 'ed'.
'on horseback' becomes 'up'.
'us'+'ed'+'up'='USED-UP'

(Other definitions for used up that I've seen before include "Consumed, finished" , "Exhausted the supply" , "Consumed completely" , "Spent" .)

I've seen this clue in The Telegraph.
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