Pops back to get juice (3)
I believe the answer is:
sap
'juice' is the definition.
(thesaurus)
'pops back' is the wordplay.
'pops' becomes 'pas' ('pa' can be a synonym of 'pop').
'back' says the letters should be written in reverse.
'pas' in reverse letter order is 'SAP'.
'to get' is the link.
(Other definitions for sap that I've seen before include "Enervate" , "Watery substance in a plant" , "One is easily fooled" , "Plant's fluid" , "Juice; energy" .)