Get on the wrong side of mule, say (5)

I believe the answer is:

cross

I believe this is a double definition.

'get on the wrong side of' is the first definition.
(as in crossing or antagonising someone)

'mule say' is the second definition.
(mules are crossbreeds)

(Other definitions for cross that I've seen before include "Vexed" , "Grouchy" , "On soccer pitch pass" , "frustrated?" , "SECOND HALF OF 9" .)

I've seen this clue in The Times.

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