Charles and Heather are obviously amused (9)

I believe the answer is:

chuckling

'obviously amused' is the definition.

'charles and heather' is the wordplay.
'charles' becomes 'chuck'.
'and' says to put letters next to each other.
'heather' becomes 'ling' (synonyms).
'chuck'+'ling'='CHUCKLING'

'are' acts as a link.

(Another definition for chuckling that I've seen is " laughing quietly".)

I've seen this clue in The Guardian.

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