monkey vs muck about

monkey is a noun but muck about is not a noun.

Word	Noun	Adjective	Verb	Adverb
monkey	Yes	No	Yes	No
muck about	No	No	Yes	No

As verbs, monkey and muck about are synonyms defined as:

monkey and muck about: do random, unplanned work or activities or spend time idly

Other synonyms of monkey include mess around, monkey around, muck around, potter, putter, tinker.

monkey (noun)	muck about (noun)
any of various long-tailed primates (excluding the prosimians)
one who is playfully mischievous

monkey (verb)	muck about (verb)
do random, unplanned work or activities or spend time idly	do random, unplanned work or activities or spend time idly
play around with or alter or falsify, usually secretively or dishonestly