Extraordinarily, achieves first in geography — follow that! (4,5)
I believe the answer is:
give chase
'follow that' is the definition.
'extraordinarily achieves first in geography' is the wordplay.
'extraordinarily' indicates an anagram (I've seen this in other clues).
'first in' indicates taking the first letters.
The initial letter of 'geography' is 'g'.
'achieves'+'g'='achievesg'
'achievesg' anagrammed gives 'GIVE CHASE'.
(Other definitions for give chase that I've seen before include "Set off in pursuit" , "pursue" , "Go after" .)