Clue: May Eden, say, tend to be found between 11 and 13? (5,9)
Answer: PRIME MINISTERS
Explanation: Definition: May Eden, say
An envelope ('to be found between') of MINISTER ('tend', verb) in PRIMES ('11 and 13′, with the question mark indicating indication by examples), with Theresa 'May' and Anthony 'Eden' likewise being examples ('say').