The sound of a pig in agreeable surroundings (4)
I believe the answer is:
oink
'the sound of a pig' is the definition.
(I've seen this before)
'in agreeable surroundings' is the wordplay.
'agreeable' becomes 'ok' (I can't justify this - if you can you should give a lot more credence to this answer).
'surroundings' is an insertion indicator.
'in' placed within 'ok' is 'OINK'.
Can you help me to learn more?
(Other definitions for oink that I've seen before include "Beastly noise" , "Cartoon sound of pig" , "Sound made by a pig" , "behave like a pig" , "farmyard noise" .)