Clue: Fine article on science fiction one cheers, with load about rising uncertainty (2,3,2,1,6)
Answer: AS FIT AS A FIDDLE
Explanation: Definition: Fine
A charade of A (indefinite 'article') plus SF ('science fictiion') plus I ('one') plus TA('cheers' in the sense of "thank you") plus SAFIDDLE, an envelope ('about') of FI, a reversal ('rising' in a down light) of IF ('uncertainty') in SADDLE ('load').