Son, given heavy responsibility, slept (9)

I believe the answer is:

slumbered

'slept' is the definition.
('slumber' can be a synonym of 'sleep')

'son given heavy responsibility' is the wordplay.
'son' becomes 's'.
'given heavy responsibility' becomes 'lumbered'.
's'+'lumbered'='SLUMBERED'

(Another definition for slumbered that I've seen is " Slept".)

I've seen this clue in The Telegraph.

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