Snigger at a soothsayer having a bit of fun! (5)
I believe the answer is:
sneer
'snigger' is the definition.
(thesaurus)
'a soothsayer having a bit of fun' is the wordplay.
'a soothsayer' becomes 'seer' (I've seen this in another clue).
'having' indicates putting letters inside.
'a bit of fun' becomes 'n' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'seer' placed around 'n' is 'SNEER'.
'at' acts as a link.
Can you help me to learn more?
(Other definitions for sneer that I've seen before include "Be derisive; Sheridan's Critic" , "Speak contemptuously" , "Show contempt by contorting the face" , "Show cynical contempt" , "Express cynical contempt" .)