Fast learner overwhelms Wimbledon’s second seed (6)
I believe the answer is:
'seed' is the definition.
(I've seen this before)
'fast learner overwhelms wimbledon's second' is the wordplay.
'fast' becomes 'lent' (Lent is a period of fasting in Christianity).
'learner' becomes 'l' (as in a learner driver with L-plates on their car).
'overwhelms' means one lot of letters goes inside another.
'wimbledon's second' becomes 'i' (2nd letter of 'wimbledon').
'lentl' going around 'i' is 'LENTIL'.
(Other definitions for lentil that I've seen before include "Pulse used in cooking" , "High-protein pulse" , "Pulse used in soup" , "Leguminous vegetable" , "Small seed used for food" .)