She’ll let you know when to turn round (6)
I believe the answer is:
stella
'she'll let you' is the definition.
I can't tell whether this defines the answer.
'know when to turn round' is the wordplay.
'know' becomes 'tell' (I am not sure about this - if you are sure you should believe this answer much more).
'when' becomes 'as' (eg 'when I walked' means 'as I walked').
'to turn' says the letters should be written backwards.
'round' means one lot of letters goes inside another.
'as' backwards is 'sa'.
'tell' put within 'sa' is 'STELLA'.
Can you help me to learn more?
(Other definitions for stella that I've seen before include "- Gibbons (Cold Comfort Farm)" , "woman" , "Swift favourite" , "Girl's name meaning star" , "Paul McCartney's daughter" .)