First sentence sounds close to a snigger (5)
I believe the answer is:
sneer
'to a snigger' is the definition.
(thesaurus)
'first sentence sounds close' is the wordplay.
I cannot really understand how this works, but
'first sentence' could be 's' (1st letter of 'sentence') and 's' is located in the answer.
The remaining letters 'neer' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for sneer that I've seen before include "Show contempt by contorting the face" , "Contemptuous look" , "Derisive remark" , "Speak contemptuously" , "Smile contemptuously" .)