... small containers containing ale finally? Not exactly ... (6)

I believe the answer is:

steins

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'not exactly' is the definition.
I can't judge whether this definition defines the answer.

'small containers containing ale finally?' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'containers' becomes 'tins' (tin is a kind of container**).
'containing' is an insertion indicator.
'finally?' says to take the final letters (I've seen 'finally' mean this).
The last letter of 'ale' is 'e'.
'tins' enclosing 'e' is 'teins'.
's'+'teins'='STEINS'

Can you help me to learn more?

(Another definition for steins that I've seen is " Large beer mugs".)

I've seen this clue in The Telegraph.

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