a peach of a

a peach of a —

a particularly excellent or desirable thing of the kind specified. informal
Peach has been used since the mid 18th century as a colloquial term for an attractive young woman and more generally since the mid 19th century for anything of exceptional quality.
1998 Spectator Neil Pollard…rode a peach of a race…to win the two-mile marathon.
See also: of, peach