Clue: Airliner emptied, a line appearing under drill on a plane, say (8)
Answer: ARBOREAL
Explanation: Definition: on a plane, say
for the definition: 'plane' is a name for a tree of the genus Platanus, so ARBOREAL='on a (for example, plane) tree' 
A-irline-R emptied of its inner letters, plus A + L (line) after BORE="drill"