Sex changes in peak spring (8)
I believe the answer is:
fountain
'spring' is the definition.
(synonyms)
'sex changes in peak' is the wordplay.
I cannot really see how this works, but
'in' is within the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for fountain that I've seen before include "Man-made water-jet" , "Artificially-produced jet of water" , "Spurt" , "Artificially produced jet of water" , "Ornamental jet of water, usually in public place" .)