Girl on stage gets small part in picture (7)
I believe the answer is:
tessera
'part in picture' is the definition.
'tessera' can be an answer for 'part' (I have seen 'Part of mosaic' mean 'tessera' so perhaps 'part' could also mean 'tessera'). I am unsure of the 'in picture' bit.
'girl on stage gets small' is the wordplay.
I cannot really understand how this works, but
'girl' could be 'tess' and 'tess' is found in the answer.
'stage' could be 'era' (I've seen this before) and 'era' is located in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for tessera that I've seen before include "Small mosaic piece" , "Small square tile used in mosaics" , "only part of the picture" , "part of a mosaic" , "password" .)