Opening place to go for pop festivals? Loves to get away (6)
I believe the answer is:
portal
'opening' is the definition.
(type of opening or entrance)
'place to go for pop festivals? loves to get away' is the wordplay.
'place to go for pop festivals?' becomes 'portaloo' (temporary toilet found at music festivals).
'loves' becomes 'oo' (love means 0 in tennis).
'to get away' is a deletion indicator.
'portaloo' with 'oo' removed is 'PORTAL'.
(Other definitions for portal that I've seen before include "'Doorway, entrance (6)'" , "An imposing gateway" , "An imposing door or gate" , "Grand and imposing entrance" , "An imposing gate or doorway" .)