Yankee with no euro to change? I accept the terms! (5,2)
I believe the answer is:
youre on
'i accept the terms' is the definition.
('you're on' can be used to agree to a challenge)
'yankee with no euro to change?' is the wordplay.
'yankee' becomes 'Y' (phonetic alphabet: alpha, bravo, charlie etc.).
'with' means one lot of letters go next to another.
'to change?' indicates anagramming the letters (I've seen 'change' mean this).
'no'+'euro'='noeuro'
'noeuro' anagrammed gives 'oureon'.
'y'+'oureon'='YOURE ON'
(Other definitions for youre on that I've seen before include "I accept the terms" , "I agree to challenge" , "I accept the offer you have made!" , "said to clinch a deal?" , "Encouraging comment" .)