Escape from capsule aka Gemini (7)
I believe the answer is:
leakage
'escape' is the definition.
(synonyms)
'from capsule aka gemini' is the wordplay.
'from' indicates the answer is hidden within the clue.
'LEAKAGE' can be found hidden inside 'capsule aka gemini'.
(Other definitions for leakage that I've seen before include "Escape of liquid - or private information" , "That which seeps out" , "Accidental (fluid) release" , "Accidental loss of fluid" , "Escaping liquid or gas" .)