One President or another turning crazy in a second (5)
I believe the answer is:
adams
'one president or another' is the definition.
(John Adams or John Quincy Adams)
'turning crazy in a second' is the wordplay.
'turning' says the letters should be written backwards.
'crazy' becomes 'mad' (synonyms).
'in' is an insertion indicator.
'second' becomes 's' (common abbreviation).
'mad' back-to-front is 'dam'.
'a'+'s'='as'
'dam' inserted inside 'as' is 'ADAMS'.
(Other definitions for adams that I've seen before include "American composer" , "Father and son US presidents" , "Name of two early US presidents" , "Presidential father or son" , "revolutionary leader" .)