Abandoned infant worrying don in gulf (9)
I believe the answer is:
foundling
'abandoned infant' is the definition.
(synonyms)
'worrying don in gulf' is the wordplay.
'worrying' indicates an anagram.
'don'+'in'+'gulf'='doningulf'
'doningulf' anagrammed gives 'FOUNDLING'.
(Other definitions for foundling that I've seen before include "Deserted child" , "Child left" , "Abandoned baby" , "Abandoned infant" , "abandoned child" .)