Assess the situation, having deadheaded pot plant (4,5)
I believe the answer is:
take stock
'assess the situation' is the definition.
(I've seen this before)
'deadheaded pot plant' is the wordplay.
'deadheaded pot' becomes 'take' (I can't explain this - if you can you should give a lot more credence to this answer).
'plant' becomes 'stock' (stock is a kind of plant).
'take'+'stock'='TAKE STOCK'
'having' is the link.
Can you help me to learn more?
(Other definitions for take stock that I've seen before include "Review a situation - assess holdings" , "as shoplifters do" , "See how the land lies" , "Make inventory or examine own position" , "Review situation or count assets" .)