Gosh, a century followed by a pair! (3)
I believe the answer is:
coo
'gosh' is the definition.
'a century followed by a pair' is the wordplay.
'a century' becomes 'C' (common abbreviation).
'followed by' is a charade indicator (letters next to each other).
'a pair' becomes 'oo' (resembles 00, a pair of ducks in cricket).
'c'+'oo'='COO'
(Other definitions for coo that I've seen before include "Soft murmuring sound of a pigeon" , "Pigeon noise" , "Surprised expression" , "Dove-like noise" , "Call like a dove" .)