A 'predicate' is the part expressing the action, typically ending in '~da' or '~suru'.
Literal
''Predicate'' [quotative-とは], action [object-を] express part [copula-で], last [subject-が] ''~da'' ''~suru'' [etc-など] [locative-に] become part is.
A textbook definition from grammar class. 述部 ('predicate part') is the Japanese grammar term for the predicate — the part of the sentence containing the verb or copula. Note the structure: noun-で (copula て-form) chains into the second clause, a typical nominal-heavy formal definition style. ~とは is the definitional topicalizer.