Clothing for the open air will last longer (7)
I believe the answer is:
outwear
'last longer' is the definition.
(I've seen this before)
'clothing for the open air will' is the wordplay.
'clothing' becomes 'wear' (synonyms).
'for' says to put letters next to each other (I've seen this in other clues).
'the open air will' becomes 'out' (I can't justify this - if you can you should believe this answer much more).
'wear' after 'out' is 'OUTWEAR'.
Can you help me to learn more?
(Other definitions for outwear that I've seen before include "ride" , "Top dressing" , "Last longer than others" , "may last longer" , "Exhaust" .)