leading, top
a leading cancer specialist

experienced, qualified, trained
independent
academic, industry, professional, research, technical
clinical, hospital, medical, public-health
cancer, ear, ear, nose and throat, eye, fertility, heart, mental-health, skin
finance, financial, marketing, property (BrE), tax
recruitment (esp. BrE)
development, education, foreign-policy, technology
a rural-development specialist

communications, computer, information-technology (abbreviated to IT), software, systems
intelligence, security
a new generation of computer security specialists

bring in, hire
They brought in an outside specialist to install the computer system.

consult, see
He went to see a cancer specialist.

specialist in
She is a specialist in children's literature.

specialist on
a specialist on the history of this city

a group of specialists, a team of specialists
a specialist in the field
The book is written by a noted specialist in the field.

Specialist is used with these nouns:
advice, editor, equipment, expertise, field, help, input, journal, knowledge, library, magazine, nature, nurse, outlet, producer, publication, publisher, qualification, reader, retailer, shop, skill, subject, surgeon, teacher, training, treatment