Il significato e' questo. Puoi rigirarla un po' come vuoi. Al link trovi la spiegazione e l'origine dell'espressione. Inizialmente usata nel gioco delle carte, ora si utilizza anche in senso figurato.

Meaning

To complete something well or successfully, especially in circumstances in which it isn't expected.

By the 18th century turn up trumps had begun to be used in its figurative sense, i.e. with no direct reference to card playing. It is recorded that way in Grose's Dictionary of the Vulgar Tongue, 1785:

"Something may turn up trumps, something lucky may happen."

http://www.phrases.org.uk/meanings/come-up-trumps.html