Gosh! A representation of carbon dioxide? (3)
I believe the answer is:
coo
'gosh' is the definition.
'a representation of carbon dioxide?' is the wordplay.
'a representation' indicates anagramming the letters.
'of' becomes 'o''.
'carbon' becomes 'C' (C is the chemical symbol for carbon).
'dioxide?' becomes 'o' (I am not sure about this - if you are sure you should believe this answer much more).
'o'+'c'='oc'
'oc' is an anagram of 'co'.
'co'+'o'='COO'
Can you help me to learn more?
(Other definitions for coo that I've seen before include "Expression of surprise (by a dove?)" , "Bill's companion" , "Make loving sounds -bill and . . ." , "Soft murmuring sound of a pigeon" , "Sound made by doves" .)