Picked up, spots United on attack (7)
I believe the answer is:
seizure
'attack' is the definition.
(synonyms)
'picked up spots united on' is the wordplay.
I cannot really see how this works, but
'united' could be 'u' and 'u' is located in the answer.
'on' could be 're' ('on' can be mean 'with reference to') and 're' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for seizure that I've seen before include "Sudden attack of illness" , "Paroxysm" , "Taking possession by legal process" , "Attack - capture" , "Taking something" .)