Uncontrolled area in the tarmac (7)
I believe the answer is:
runaway
'uncontrolled' is the definition.
(similar in meaning)
'area in the tarmac' is the wordplay.
'area' becomes 'a' (maths abbreviation).
'in' means one lot of letters goes inside another.
'the tarmac' becomes 'runway' (I've seen this in another clue).
'a' inserted into 'runway' is 'RUNAWAY'.
(Other definitions for runaway that I've seen before include "One who has taken flight" , "such a success?" , "Fugitive" , "Absconder" , "refugee?" .)