Clematis armandii

I have a two-year-old clematis which I have tended carefully. In its second year it has grown really well, but unfortunately missed out on watering for a fortnight in August.

It hasn't perked up since my return. The final section of new growth and the leaves nearest the base have died and the rest of the plant looks like it's heading the same way. 

Should I cut it back and hope for regrowth next year? Any advice would be great.

Thanks