Outside playing on a pier (4-3)
I believe the answer is:
open air
'outside' is the definition.
(similar in meaning)
'playing on a pier' is the wordplay.
'playing' indicates anagramming the letters.
'on'+'a'+'pier'='onapier'
'onapier' with letters rearranged gives 'OPEN-AIR'.
(Other definitions for open air that I've seen before include "Outdoor" , "Out-of-doors" , "like 12 [CONCERT] in Hyde Park" , "kind of concert" , "Outside" .)