Yen's calamitous slide returns (6)
I believe the answer is:
yields
'returns' is the definition.
('yield' can be a synonym of 'return')
'yen's calamitous slide' is the wordplay.
'yen' becomes 'y'.
'calamitous' is an anagram indicator.
'slide' with letters rearranged gives 'ields'.
'y'+'ields'='YIELDS'
(Other definitions for yields that I've seen before include "Investment returns" , "Gives way, surrenders" , "Succumbs" , "Submits" , "Produces or gives in" .)