Flight circling southern airspace trials bombing (6,9)
I believe the answer is:
spiral staircase
'flight' is the definition.
(I've seen this before)
'circling southern airspace trials bombing' is the wordplay.
'circling' indicates putting letters inside (circling can mean going around or containing).
'southern' becomes 's' (abbreviation).
'bombing' is an anagram indicator.
'airspace'+'trials'='airspacetrials'
'airspacetrials' anagrammed gives 'spiraltaircase'.
's' inserted within 'spiraltaircase' is 'SPIRAL STAIRCASE'.
(Another definition for spiral staircase that I've seen is " Not a direct flight".)