A trip and it's back in the old routine, love! (4)
I believe the answer is:
tour
'a trip' is the definition.
(a journey or expedition)
'it's back in the old routine love' is the wordplay.
'it' becomes ''t' (abbreviation. e.g. in 'tis).
'back in the old routine love' becomes 'our' (I am not sure about this - if you are sure you should believe this answer much more).
't'+'our'='TOUR'
'and' acts as a link.
Can you help me to learn more?
(Other definitions for tour that I've seen before include "Drive" , "Journey round" , "Visit a number of places" , "Extended journey" , "Entertainer's itinerary" .)