Unexpectedly convert cheat (5-6)

I believe the answer is:

short change

'cheat' is the definition.
(I've seen this before)

'unexpectedly convert' is the wordplay.
'unexpectedly' becomes 'short' (as in 'to be caught short').
'convert' becomes 'change' (synonyms).
'short'+'change'='SHORT-CHANGE'

(Other definitions for short change that I've seen before include "Cheat" , "Rip off" , "swindle" , "Dish" .)

I've seen this clue in The Telegraph.

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