Car is secure outside front of terminal (5)
I believe the answer is:
motor
'car' is the definition.
(motor can informally mean a car)
'secure outside front of terminal' is the wordplay.
'secure' becomes 'moor' (mooring is a kind of securing).
'outside' means one lot of letters goes inside another.
'front of' indicates taking the first letters.
The initial letter of 'terminal' is 't'.
'moor' placed around 't' is 'MOTOR'.
'is' is the link.
(Other definitions for motor that I've seen before include "Driver" , "Engine - relating to movement" , "Move fast" , "Drive" , "Car (colloq,)" .)