Loss of earnings shocking to Mexican (6,3)
I believe the answer is:
income tax
'loss of earnings' is the definition.
'shocking to mexican' is the wordplay.
'shocking' indicates anagramming the letters (I've seen this in other clues).
'to'+'mexican'='tomexican'
'tomexican' anagrammed gives 'INCOME-TAX'.
(Other definitions for income tax that I've seen before include "Subject of 17, 8 [CHANCELLORS STATEMENT]" , "state levy" , "not what one takes home?" , "What must be paid following return" , "Part of earnings lost?" .)