As an alternative to a group of spacemen (4)
I believe the answer is:
nasa
'to a group of spacemen' is the definition.
I can't judge whether this defines the answer.
'as an alternative' is the wordplay.
'alternative' indicates anagramming the letters.
'as'+'an'='asan'
'asan' with letters rearranged gives 'NASA'.
Can you help me to learn more?
(Other definitions for nasa that I've seen before include "rocket launcher" , "US agency responsible for space flight" , "US headquarters for space exploration" .)