Popular teams showing guts (7)
I believe the answer is:
insides
'guts' is the definition.
(thesaurus)
'popular teams' is the wordplay.
'popular' becomes 'in'.
'teams' becomes 'sides' (I've seen this before).
'in'+'sides'='INSIDES'
'showing' is the link.
(Other definitions for insides that I've seen before include "stomach" , "Entrails" , "guts" .)