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 a hidden word.
'LEAKAGE' is hidden in the letters of '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" .)