Add small measure of spirits (3)

I believe the answer is:

tot

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This could be a double definition.

'add small' is the first definition.
'tot' can be an answer for 'add' (synonyms). I am unsure of the 'small' bit.

'measure of spirits' is the second definition.
(I've seen this before)

Can you help me to learn more?

(Other definitions for tot that I've seen before include "quick drink" , "nipper" , "A wee dram" , "Calculate" , "Spirit measure" .)

I've seen this clue in The Times and The Sun.

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