Clue: Place for knocking shop at the back: make love with rest when light goes on (8)
Answer: DOORSTEP
Explanation: Definition: Place for knocking
A charade of DO ('make') plus O ('love') plus RSTE, an anagram ('when light'?) of 'rest' plus P ('sho**P** at the back'). 'Goes on' indicates the order of the particles, in a down light.