Girl taking dog maybe the wrong way — an error (7)
I believe the answer is:
misstep
'an error' is the definition.
(misstep can mean an error or mistake)
'girl taking dog maybe the wrong way' is the wordplay.
'girl' becomes 'miss' (term of address for an unmarried woman).
'taking' says to put letters next to each other.
'dog maybe' becomes 'pet' (dogs are often kept as pets).
'the wrong way' says the letters should be written in reverse.
'pet' reversed gives 'tep'.
'miss'+'tep'='MISSTEP'
(Other definitions for misstep that I've seen before include "bad move" , "Badly judged move" , "Badly judged footing" , "Error" , "False move" .)