Cricket perhaps, has time and energy to make reproductive contribution (6)
I believe the answer is:
gamete
'make reproductive contribution' is the definition.
Although both the answer and definition are singular nouns, I can't understand how one could define the other.
'cricket perhaps has time and energy' is the wordplay.
'cricket perhaps' becomes 'game' (cricket is a kind of game).
'has' says to put letters next to each other.
'time' becomes 't' (abbreviation).
'and' is a charade indicator (letters next to each other).
'energy' becomes 'e' (physics symbol as in E=mca).
'game'+'t'+'e'='GAMETE'
'to' acts as a link.
Can you help me to learn more?
(Other definitions for gamete that I've seen before include "Egg-cell" , "An egg or sperm cell" , "Germ cell in reproduction" , "Reproductive cell" , "something seedy?" .)