Measure of resistance as I am exercising west of Lambeth walk? (9)

I haven't cracked this one yet — but the brilliant team at Times for the Times have:

I’M (I am), PE (exercising), DANCE (Lambeth walk). ‘West of’ is a juxtaposition indicator. There’s an argument that ‘walk’ should be capitalised here since it’s part of the name of a real street in London as referenced in the song Lambeth Walk and the Cockney dance of the same name. Both featured in the 1937 stage musical Me and My Girl by Noel Gay with book and lyrics by Douglas Furber and L. Arthur Rose. In the 1980s the show was revived with a new book by Stephen Fry and ran successfully in the West End, on Broadway and toured for many years. It’s reputed to be where Fry made his first million. I won’t post a link to the tune as its a real earworm and you’ll be cursing me all day.