Possible Clues:

• Colleague has a lot of cannabis after work
• Pilot goes hither and thither to find China
• Opposite number (colloq.)
• Whichever way you move, it's mate
• Colleague (colloq.)
• One's counterpart at work on the river
• Counterpart works back to back
• Research on a rival, briefly
• The other side, for short
• Research on an adversary, for short