Travelling costumes in stretch cases (10)

I believe the answer is:

spacesuits

'travelling costumes' is the definition.
(costumes worn in space)

'stretch cases' is the wordplay.
'stretch' becomes 'space' (stretch can mean an area of space).
'cases' becomes 'suits' ('suit' can be a synonym of 'case').
'space'+'suits'='SPACESUITS'

'in' acts as a link.

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.