Man reversed into drive-in restaurant (5)
I believe the answer is:
ernie
'man' is the definition.
(I've seen this before)
'reversed into drive-in restaurant' is the wordplay.
'reversed' says the letters should be written in reverse.
'into' says the answer is hidden in the clue.
'einre' is hidden within 'drive in restaurant'.
'einre' back-to-front is 'ERNIE'.
(Other definitions for ernie that I've seen before include "Selector of winning premium bond numbers" , "Sergeant Bilko, for one" , "Wise for instance" , "National Savings computer" , "Machine that randomly selects Premium Bond winners" .)