Group of big cats from Portugal mix in prominent position (5,2,5)
I believe the answer is:
pride of place
'prominent position' is the definition.
(things in pride of place are displayed prominently)
'group of big cats from portugal mix in' is the wordplay.
'group of big cats' becomes 'pride' (group of lions).
'from' becomes 'of' (of can mean from or belonging to).
'portugal' becomes 'p' (common abbreviation eg on car number plates).
'mix in' becomes 'lace' (as in lacing a drink with something).
'pride'+'of'+'p'+'lace'='PRIDE OF PLACE'
(Other definitions for pride of place that I've seen before include "Most honourable position" , "Most prominent position" , "Patriotism" , "that the kings of beasts take?" , "The best spot" .)