Astronomer, female, beginning to investigate constellation (7)
I believe the answer is:
galileo
'astronomer' is the definition.
(I've seen this before)
'female beginning to investigate constellation' is the wordplay.
'female' becomes 'gal' (gal is a kind of female).
'beginning to' indicates taking the first letters.
'constellation' becomes 'Leo' (Leo is an example).
The initial letter of 'investigate' is 'i'.
'gal'+'i'+'leo'='GALILEO'
(Other definitions for galileo that I've seen before include "He said Eppur si muove (But it does move)" , "Great Italian astronomer and physicist of 17th century, suppressed by Church" , "Refracting telescope inventor" , "Astronomer - ogle Ali (anag)" , "was in trouble with the Inquisition" .)