### Clue: Difficult today to accept note on Swift being inflexible (4-3-4)
### Answer: HARD-AND-FAST 
 ### Explanation: Definition: inflexible
 HARD(difficult, as in "a hard/difficult crossword", say) + [ AD(abbrev. for "anno Domini", an abbrev. used with a date, strictly a year, indicating a relatively more recent time;today used loosely) **containing**(to accept) N(abbrev. for "note") ] **plus**(on) FAST(swift;fleet).