Gold initially like hydrogen, say? (3)
I believe the answer is:
gas
'hydrogen say?' is the definition.
(hydrogen is a kind of gas)
'gold initially like' is the wordplay.
'initially' suggests taking the first letters.
'like' becomes 'as'.
The first letter of 'gold' is 'g'.
'g'+'as'='GAS'
(Other definitions for gas that I've seen before include "See 2" , "Chat (colloq.)" , "Domestic fuel" , "person who's amusing ..." , "Hydrogen possibly" .)