Reportedly choose underwear for alfresco diners! (10)

I believe the answer is:

picnickers

I'm a little stuck... Click here to teach me more about this clue!

'alfresco diners' is the definition.
(people eating in the open air)

'reportedly choose underwear' is the wordplay.
'reportedly' shows a homophone (sound like).
'choose' becomes 'pick' (picking is a kind of choosing).
'underwear' becomes 'nickers' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'pick' sounds like 'pic'.
'pic'+'nickers'='PICNICKERS'

'for' acts as a link.

Can you help me to learn more?

I've seen this clue in The Telegraph.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.