Sauce unfortunately knocked over covers son (5)
I believe the answer is:
salsa
'sauce' is the definition.
(I've seen this before)
'unfortunately knocked over covers son' is the wordplay.
'unfortunately' becomes 'alas' (I've seen this before).
'knocked over' says the letters should be written in reverse.
'covers' indicates putting letters inside.
'son' becomes 's'.
'alas' written backwards gives 'sala'.
'sala' placed around 's' is 'SALSA'.
(Other definitions for salsa that I've seen before include "Latin-American dance" , "Cuban dance music or spicy sauce" , "The Latin-American sound" , "dressing" , "Sauce; Afro-Cuban dance" .)