adjective

(of a task) requiring much skill or effort.

she has a busy and demanding job

difficult,challenging,testing,taxing,exacting,tough,hard,onerous,burdensome,stressful,formidable,arduous,tiring,wearing,exhausting,wearying,wearisome,draining,uphill,rigorous,gruelling,back-breaking,Herculean,punishing,a tall order,knackering,toilsome