Tangle as some girl ran sneakily uphill (7)
I believe the answer is:
ensnarl
'tangle' is the definition.
(I know that ensnarl is a more specific form of tangle)
'some girl ran sneakily uphill' is the wordplay.
'some' indicates the answer is hidden within the clue (some parts of the word are used).
'uphill' says the letters should be written in reverse (in a down clue, letters go up).
'lransne' can be found hidden inside 'girl ran sneakily'.
'lransne' written backwards gives 'ENSNARL'.
'as' is the link.
(Other definitions for ensnarl that I've seen before include "put into difficulty?" , "To embroil" .)