Certainly not a hundred drunk by spy, single glass (7)

I believe the answer is:

monocle

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'single glass' is the definition.
'monocle' can be an answer for 'glass' (I've seen this before). I'm not certain of the 'single' bit.

'certainly not a hundred drunk by spy' is the wordplay.
'certainly not' becomes 'no'.
'a hundred' becomes 'C' (Roman numeral).
'drunk by' is an insertion indicator.
'spy' becomes 'mole' (mole is a kind of spy).
'no'+'c'='noc'
'noc' inserted inside 'mole' is 'MONOCLE'.

Can you help me to learn more?

(Other definitions for monocle that I've seen before include "lens" , "Single eyeglass" , "Reading glass for one eye only" , "optical device" , "One-lens seeing apparatus" .)

I've seen this clue in The Telegraph.

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