Many may have been a star! (5)
I believe the answer is:
deneb
'star' is the definition.
(I've seen this before)
'many may have been a' is the wordplay.
I cannot really see how this works, but
'many' could be 'd' and 'd' is located in the answer.
an anagram of 'been' is 'eneb' which is located in the answer.
No letters remain.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for deneb that I've seen before include "Be Ned (anag) - brightest star in Cygnus" , "First magnitude star in Cygnus" , "The star Alpha Cygni" , "Bright star; be end (anag.)" , "Bright star in Cygnus" .)