Conjunctive pronouns (who, what, whose, which) not only point back to some person or thing mentioned before but also have conjunctive power, introducing subordinate clauses (subject clauses, object clauses, predicative clauses).

What June had taken for personal interest was only the impersonal excitement of every Forsyte… (Galsworthy) (SUBJECT CLAUSE)

What you want, in fact, is a first-rate man for a fourth-rate fee, and that’s exactly what you’ve got! (Galsworthy) (PREDICATIVE CLAUSE)

I don’t want to hear what you’ve come for. (Galsworthy) (OBJECT CLAUSE)

In the clause they introduce they perform different functions, those of subject, predicative, attribute, object.

What had made her yield he could never make out; and from Mrs. Heron, a woman of some diplomatic talent, he learnt nothing. (Galsworthy) (SUBJECT)

Erik realized with a sinking sensation that Haviland didn’t know who he was. (Wilson)(PREDICATIVE)

I’ve spent a lot of time in the chart-room now, and I’m on the edge of knowing my way about, what charts I want to refer to, what coasts I want to explore. (London) (ATTRIBUTE)

What Savina could no longer do for him, he did himself, and brutally brushed aside all other interests except her. (Wilson) (OBJECT)