Loyal toast drunk in hock, presumably (6)

I believe the answer is:

pledge

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'hock presumably' is the definition.
'pledge' can be an answer for 'hock' (thesaurus). I'm not certain of the 'presumably' bit.

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for pledge that I've seen before include "Vow; security" , "Promise, word of honour" , "assurance" , "Promise solemnly and formally" , "Promise - security" .)

I've seen this clue in The Guardian and The Irish Independent.

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