Vet covers places with variable rate (8)
I believe the answer is:
velocity
'rate' is the definition.
(I know that velocity is a type of rate)
'vet covers places with variable' is the wordplay.
'covers' indicates putting letters inside.
'places with' becomes 'loci' (I've seen this before. I am not sure about the 'with' bit.).
'variable' becomes 'y' (algebra).
'vet' going around 'loci' is 'velocit'.
'velocit'+'y'='VELOCITY'
Can you help me to learn more?
(Other definitions for velocity that I've seen before include "Rate of motion, distance per unit of time" , "Rate of movement." , "Distance travelled per unit of time" , "Swiftness" , "Agreeable -- Riviera resort" .)