Fast over slow (5)
I believe the answer is:
lento
'slow' is the definition.
(similar in meaning)
'fast over' is the wordplay.
'fast' becomes 'lent' (Lent is a period of fasting in Christianity).
'over' becomes 'o' (cricket abbreviation).
'lent'+'o'='LENTO'
(Other definitions for lento that I've seen before include "Musically low speed" , "It's slower than adagio" , "How one scores slowly" , "(When playing music) slowly" , "(Of tempo) slow" .)