Footballer, unusually agile, catching ball? (6)
I believe the answer is:
goalie
'footballer' is the definition.
(goalkeeper)
'unusually agile catching ball?' is the wordplay.
'unusually' is an anagram indicator.
'catching' means one lot of letters goes inside another.
'ball?' becomes 'o' (O looks like a ball).
'agile' anagrammed gives 'galie'.
'galie' enclosing 'o' is 'GOALIE'.
(Other definitions for goalie that I've seen before include "one saves" , "On-field custodian" , "Hart perhaps" , "Soccer player who protects the target" , "Football team member" .)