One sort of solution to the aliens problem (6)
I believe the answer is:
saline
'one sort of solution' is the definition.
(I've seen this in another clue)
'the aliens problem' is the wordplay.
'problem' indicates an anagram.
'aliens' anagrammed gives 'SALINE'.
'to' acts as a link.
(Other definitions for saline that I've seen before include "solution" , "Salty like sea water" , "Intravenous feeding" , "Containing or tasting of salt" , "Like seawater" .)