Church taking measure of current title-holder (5)
I believe the answer is:
champ
'title-holder' is the definition.
(synonyms)
'church taking measure of current' is the wordplay.
'church' becomes 'ch' (abbreviation on maps etc).
'taking' says to put letters next to each other.
'measure of current' becomes 'amp' (I've seen this in other clues).
'ch'+'amp'='CHAMP'
(Other definitions for champ that I've seen before include "boxer who is top dog?" , "Fret impatiently; winner" , "Supreme competitor" , "use teeth?" , "first place" .)