Big band playing around Long Island, performing without rehearsal (2-7)
I believe the answer is:
ad-libbing
'performing without rehearsal' is the definition.
(an ad-lib is an improvised line)
'big band playing around long island' is the wordplay.
'playing' indicates an anagram.
'around' means one lot of letters goes inside another.
'long' becomes 'l'.
'island' becomes 'i' (geographical abbreviation).
'big'+'band'='bigband'
'bigband' is an anagram of 'adbbing'.
'l'+'i'='li'
'adbbing' enclosing 'li' is 'AD-LIBBING'.
(Other definitions for ad-libbing that I've seen before include "Improvising" , "Speaking without preparation" .)