False alarm – drinking spirit insignificant (8)
I believe the answer is:
marginal
'insignificant' is the definition.
(thesaurus)
'false alarm drinking spirit' is the wordplay.
'false' is an anagram indicator.
'drinking' means one lot of letters goes inside another (inserted letters are consumed or drunk).
'spirit' becomes 'gin' (alcoholic spirit).
'alarm' with letters rearranged gives 'maral'.
'maral' placed around 'gin' is 'MARGINAL'.
(Other definitions for marginal that I've seen before include "having small majority at risk" , "unsafe seat" , "Peripheral in alarming way" , "on border" , "Alarming (anag) - too small to matter" .)