Awful conservatories scorned by seniors who really ham it up (7)

I believe the answer is:

overact

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'ham it up' is the definition.
(as in a ham actor)

I don't understand the remainder of the clue.

(Other definitions for overact that I've seen before include "Do what ham thespian does" , "Ham (on stage)" , "In part, fail to convince" , "Exaggeratedly perform a role" , "Be unsubtle on stage" .)

I've seen this clue in The Irish Times.

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