Crossword Genius

Unpleasant aftermath hidden by Callaghan government (8)

Ross

I believe the answer is:

hangover

I'm a little stuck... Click here to teach me more about this clue!

'unpleasant aftermath' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.

'hidden by callaghan government' is the wordplay.
'hidden' indicates a hidden word.
'HANGOVER' is hidden in the letters of 'by callaghan government'.

Can you help me to learn more?

(Other definitions for hangover that I've seen before include "Morning-after problem" , "morning-after feeling?" , "Effect of previous day's alcohol" , "problem arising?" , "After-effects of excessive drinking" .)

I've seen this clue in The Irish Times.
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