From Longman Dictionary of Contemporary Englishmuck something ↔ out phrasal verb British EnglishTAHBAto clean the place where a farm animal lives You have to muck out the stables every day in the winter. → muck→ See Verb table
Examples from the Corpus
muck out• The acid cuts into the limestone and makes holes that, over the years, fill with muck.• Who was mucking him out and hosing him down? 