Lying low, abruptly decoy leader (7)
I believe the answer is:
lurking
'lying low' is the definition.
'decoy leader' is the wordplay.
'decoy' becomes 'lur' (I can't justify this - if you can you should give a lot more credence to this answer).
'leader' becomes 'King' (King is an example).
'lur'+'king'='LURKING'
'abruptly' is the link.
This may not be right. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for lurking that I've seen before include "Waiting in ambush" , "Lying in wait, ready to ambush perhaps" , "In hiding for ambush" , "Skulking" , "Lying in wait, to ambush say" .)