### Clue: Pressure on singers to hold new nationalist flag (6)
### Answer: PENNON 
 ### Explanation: Definition: flag
 P(abbrev. for "pressure" in physics) **placed above**(on, in a down clue) [ ENO(abbrev. for the English National Opera, company of singers) **containing**(to hold) N(abbrev. for "new") ] + N(abbrev. for "nationalist").
Defn: … in a tapered, triangular or swallow-tailed shape.