Only pretend to be hearty (5)

I believe the answer is:

bluff

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This could be a double definition.

'only pretend' is the first definition.
'bluff' can be an answer for 'pretend' (thesaurus). I am not sure about the 'only' bit.

'be hearty' is the second definition.
(thesaurus)

'to' acts as a link.

Can you help me to learn more?

(Other definitions for bluff that I've seen before include "Deceive by concealing weakness" , "Attempt to deceive" , "Steep bank; pretend confidence" , "Frank, direct; steep cliff" , "Rocky outcrop" .)

I've seen this clue in The Globe and Mail.

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