Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
step-up is a noun meaning "the act of increasing something". It carries one recorded sense.
the act of increasing something
“he gave me an increase in salary”
Definitions, synonyms and semantic relations for step-up come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.