Spotted former US president at party being held (5-3)
I believe the answer is:
polka-dot
'spotted' is the definition.
(I've seen this before)
'us president at party being held' is the wordplay.
'us president' becomes 'polk' (I've seen this in other clues).
'party' becomes 'do' (do is a kind of party).
'being held' indicates putting letters inside.
'at' going around 'do' is 'adot'.
'polk'+'adot'='POLKA-DOT'
'former' acts as a link.
This may not be correct. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for polka-dot that I've seen before include "(Of fabric) covered in small, circular regularly-spaced spots" , "Patterned with large spots" .)