be no mean (something)
To be considerably important, difficult, or noteworthy. Said of things that are not trivial or easy to obtain. Defeating an incumbent president is no mean feat, but we feel confident that our candidate has what it takes. You should be proud: placing in the top five at an Olympic event is no mean accomplishment.
be no mean...
(approving) be a thing of a very high quality; be a very good example of something: His mother was a painter and he’s no mean artist himself.Cycling around France at the age of 75 is no mean feat.