Pace of favourite's excessively strong, on reflection (8)
I believe the answer is:
footstep
'pace' is the definition.
(I know that pace can be written as footstep)
'favourite's excessively strong on reflection' is the wordplay.
'favourite's' becomes 'pet's' ('pet' can be a synonym of 'favourite').
'excessively' becomes 'too' (to too great a degree).
'strong' becomes 'f' (musical symbol for 'forte', 'strong' in Italian).
'on reflection' is a reversal indicator.
'pets'+'too'+'f'='petstoof'
'petstoof' backwards is 'FOOTSTEP'.
'of' is the link.
(Other definitions for footstep that I've seen before include "Sound of a step of someone walking" , "Sound of walker" , "Mark made when walking" , "Sound of a pace" .)