Spa got alternative power as temporary measure (7)
'temporary measure' is the definition.
(I've seen this before)
'spa got alternative power' is the wordplay.
'alternative' indicates anagramming the letters.
'power' becomes 'p'.
'spagot' is an anagram of 'stopga'.
'as' is the link.
(Other definitions for stopgap that I've seen before include "Temporary fix" , "Temporary measure" , "caretaker" , "Makeshift" , "A temporary substitute or solution" .)