'Ample' librarian, all over the place as a dancer (5,9)
I believe the answer is:
prima ballerina
'a dancer' is the definition.
(prima ballerina is a kind of dancer)
'ample librarian all over the place' is the wordplay.
'all over the place' indicates an anagram.
'ample'+'librarian'='amplelibrarian'
'amplelibrarian' with letters rearranged gives 'PRIMA BALLERINA'.
'as' is the link.
(Other definitions for prima ballerina that I've seen before include "athletic star" , "Chief female dancer" .)