My kenmore washer wont drain and agitate?

Question:it fills with water but wont drain and agitate,causeing the washer to run over..model # 110.20722990 serial # ck 08604464 type 111 kenmore 70 series

Answers:
It could be the clutch although when that happened with mine the repairman had to replace a little plastic piece that cost about $19.00.