Former president seen in mob -- amazing! (5)
I believe the answer is:
obama
'former president' is the definition.
(I've seen this before)
'in mob amazing' is the wordplay.
'in' says the answer is hidden in the clue.
'OBAMA' is hidden in the letters of 'mob amazing'.
'seen' is the link.
(Other definitions for obama that I've seen before include "in the White House" , "Politician" , "US presidential candidate" , "American president" , "Leading man" .)