Words from groom perhaps about one tense ass (5)
I believe the answer is:
idiot
'ass' is the definition.
(I know that ass can be written as idiot)
'words from groom perhaps about one tense' is the wordplay.
'words from groom perhaps' becomes 'I do' (wedding vows).
'about' means one lot of letters goes inside another.
'one' becomes 'i' (Roman numeral).
'tense' becomes 't' (grammatical abbreviation).
'ido' placed around 'i' is 'idio'.
'idio'+'t'='IDIOT'
(Other definitions for idiot that I've seen before include "Dostoevsky hero" , "Silly ass" , "Moron, fool" , "Blockhead" , "Goose" .)