Girl in front of garage coming forth (8)
I believe the answer is:
sallying
'girl in front of garage coming forth' is the definition.
I can't tell whether this definition defines the answer.
'girl in front of garage coming forth' is the wordplay.
'girl' becomes 'sally' (girl's name).
'in front of' means one lot of letters go next to another (some letters go in front of others).
'garage coming forth' becomes 'ing' (I can't explain this - if you can you should believe this answer much more).
'sally'+'ing'='SALLYING'
Can you help me to learn more?
(Another definition for sallying that I've seen is " going forth".)