Co-pilots moan flying worldwide (12)
I believe the answer is:
cosmopolitan
'worldwide' is the definition.
(synonyms)
'co-pilots moan flying' is the wordplay.
'co-pilots' becomes 'copilots' ('copilot' can be a synonym of 'co-pilot').
'flying' indicates anagramming the letters (letters fly around into new positions).
'copilots'+'moan'='copilotsmoan'
'copilotsmoan' with letters rearranged gives 'COSMOPOLITAN'.
(Other definitions for cosmopolitan that I've seen before include "Citizen of the world" , "Familiar with many cultures" , "Familiar with different cities and cultures" , "At ease in many different cultures" , "international" .)