Fool blocking inventions made for girls (7)
I believe the answer is:
lassies
'for girls' is the definition.
(lassie is a kind of girl)
'fool blocking inventions' is the wordplay.
'fool' becomes 'ass' (both can mean a stupid person).
'blocking' means one lot of letters goes inside another (to block can mean to plug a gap in something).
'inventions' becomes 'lies' (I've seen this in another clue).
'ass' going into 'lies' is 'LASSIES'.
'made' acts as a link.
(Other definitions for lassies that I've seen before include "Wee Scottish girls" , "Young women" .)