Thanks also to Hagleymum for the COAX answer. Also again to Kirky for the Aquino explanation which I'm happy to go along with - it didn't help me mistakenly pronouncing it "A-KWEE-NO"!
Agreed, Stockie. One thing about 52ac (AQUINO): I have always assumed that if the clue says "an" then that is what is in the answer and if the setter wants "a" (as here), the clue has to be set in such a way that it includes "a" rather than "an".