Sentence:  So the only strategy likely to hurt Clegg in those circumstances involves arguing that the Lib Dems are part of the mould too – not <WSD>cleanskins</WSD>, but a party with 60-plus MPs in that last discredited parliament. 
Meaning of the word marked with <WSD> tags:  Someone with no prior criminal record, a person with no previous convictions; loosely, someone who has not done anything wrong before, an unblemished character.