Long time after old Papa Haydn’s works? (5)

I believe the answer is:

opera

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'haydn's works?' is the definition.
'opera' can be an answer for 'works?' ('opera' is an alternative plural of 'opus'). I am not certain of the 'haydn's' bit.

'long time after old papa' is the wordplay.
'long time' becomes 'era' (a long period of time).
'after' says to put letters next to each other.
'old' becomes 'o' (abbreviation as in OT - Old Testament).
'papa' becomes 'P' (NATO phonetic alphabet).
'o'+'p'='op'
'era' put after 'op' is 'OPERA'.

Can you help me to learn more?

(Other definitions for opera that I've seen before include "Eg, La forza del destino" , "Carmen, for instance" , "Musical 11 across" , "Stage entertainment" , "La Traviata or Tosca, say" .)

I've seen this clue in The Times.

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