Former pupil pinching teacher’s last globe (3)
I believe the answer is:
orb
'globe' is the definition.
(I know that globe can be written as orb)
'former pupil pinching teacher's last' is the wordplay.
'former pupil' becomes 'OB' (abbreviation for 'Old Boy').
'pinching' means one lot of letters goes inside another (taking inside).
'last' suggests the final letters.
The final letter of 'teacher' is 'r'.
'ob' going around 'r' is 'ORB'.
(Other definitions for orb that I've seen before include "Jewelled ornament" , "Item of insignia" , "Sovereign artefact" , "Sphere - eye" , "A sphere or globe" .)