Walk goes so badly with dog upset? (5-4)

'walk' is the definition.
(goose step is a kind of walk)

'goes so badly with dog upset?' is the wordplay.
'badly' indicates anagramming the letters (letters in the wrong order).
'with' is a charade indicator (letters next to each other).
'dog' becomes 'pet' (dogs are often kept as pets).
'upset?' says the letters should be written in reverse (I've seen 'upset' mean this).
'pet' in reverse letter order is 'tep'.
'goes'+'so'='goesso'
'goesso' with letters rearranged gives 'gooses'.
'gooses'+'tep'='GOOSE-STEP'