1
general::
Phrase(s): camp it up
[for performers] to overact or behave in an affected manner. • The cast began to camp it up in the second act, and the critics walked out. (Fixed order.) • There is no need to camp it up. Play it the way it was written.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Make an extravagant, affected, or vulgar display, as in Amateur actors often camp it up, trying to be more dramatic. Originating in the 1950s as slang for flamboyant behavior stereotypically associated with gay men, this term began to be used more loosely by about 1970. Also see HAM IT UP.
American Heritage Idioms