Raleigh Ramper R-1027 pedal crank?

[da case]

I have a Raleigh Rampar as stated above. the left pedal seems to have quite a bit of play in it. It moves back an forth about a quater to a half inch without cranking the chain. Best was to describe it is the pedal or crank has play in it. can anyone help me diagnose this and or fix it? thanks alot