### Clue: What Robert Catesby became after going around Spain regularly (6)
### Answer: PAPIST 
 ### Explanation: Definition: What Robert Catesby became
 PAST(after, say, a certain point in time) **containing**(going around) **the 2nd and 4th letters of**(… regularly) "Spain".
Answer: A usually derogative term, as used by Protestants, for a Roman Catholic, which Robert Catesby was during Protestant King James I's reign in England.