Pace and power in germ (5)
I believe the answer is:
speed
'pace' is the definition.
(I know that speed is a type of pace)
'power in germ' is the wordplay.
'power' becomes 'p' (symbol in physics).
'in' means one lot of letters goes inside another.
'germ' becomes 'seed' (synonyms).
'p' going into 'seed' is 'SPEED'.
'and' is the link.
(Other definitions for speed that I've seen before include "Hasten" , "Rate of progress" , "Move quickly (and illegally?)" , "Rapidity of movement" , "Dispatch" .)