Father emphatic he is leaving footpath (8)
I believe the answer is:
pavement
'footpath' is the definition.
(I've seen this before)
'father emphatic he is leaving' is the wordplay.
'father' becomes 'pa' (pa is a kind of father).
'emphatic' becomes 'vehement' (I've seen this before).
'is leaving' indicates named letters should be taken away.
'vehement' with 'he' taken away is 'vement'.
'pa'+'vement'='PAVEMENT'
(Other definitions for pavement that I've seen before include "Roadside walkway" , "Raised footway by road" , "Area for pedestrians" , "Walkway by road" , "Angel --- (J B Priestley)" .)