db={"department":[{_id:1,name:"something",department:"management",employees:[{_id:1,name:"joe",suspended:false},{_id:2,name:"clare",suspended:false},{_id:3,name:"michelle",suspended:true}]}]}

db.department.aggregate([{$match:{name:"something"}},{$addFields:{employees:{$filter:{input:"$employees",cond:{$ne:["$$this.suspended",false]}}}}}])