Green’s Dictionary of Slang

no-user n.

[SE no use + sfx -er]

(Irish/Scot.) a failure, a ‘loser’.

[Scot]M. Munro Patter 49: no-user A shiftless or useless person.
[Ire](con. 1945) S. McAughtry Touch and Go 111: He was put up to me as a bit of a no-user, watch him, Dicky.