Squeal about fine increasing (8)
I believe the answer is:
Here is my best explanation:
'increasing' is the definition.
(swelling is a kind of increasing)
'squeal about fine' is the subsidiary indication.
'squeal' becomes 'sing' (both can mean to act as an informant).
'about' means one lot of letters goes inside another.
'fine' becomes 'well' ('well' can be similar in meaning to 'fine'**).
'sing' going around 'well' is 'swelling'.
(Other definitions for swelling that I've seen before include "increasing in volume", "Lump", "Growth", "Tumour", "area suffering inflation", "Abnormal enlargement", "Nodule", "growing" and "getting bigger".)