Dog expressed relief, picked up when it's time to be home (6)
I believe the answer is:
curfew
'when it's time to be home' is the definition.
(time by which people must go home)
'dog expressed relief picked up' is the wordplay.
'dog' becomes 'cur' (cur is a kind of dog).
'expressed relief' becomes 'phew' (word said as an expression of relief).
'picked up' indicates a 'sounds like' (homophone) clue.
'phew' sounds like 'few'.
'cur'+'few'='CURFEW'
(Other definitions for curfew that I've seen before include "Regulation restricting movement after certain time" , "Requirement to be indoors at a set hour" , "when it's time to go home" , "Early bedtime imposed by military" , "Early closing time imposed by military" .)