From Longman Dictionary of Contemporary Englishnot/never be one to do somethingnot/never be one to do somethinginformalNOT DO something to never do a particular thing, because it is not part of your character to do it Tom is not one to show his emotions. → one
Examples from the Corpus
not/never be one to do something• I never was one to collect a bunch of guitars like some people do.• Tom is not one to show his emotions. 