Very regularly catches fever, getting increasingly woozy (6)
I believe the answer is:
vaguer
'increasingly woozy' is the definition.
I can't judge whether this definition defines the answer.
'very regularly catches fever' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
'catches' is an insertion indicator.
'fever' becomes 'ague' (illness causing fever).
The alternating letters of 'very' are 'vr'.
'vr' placed around 'ague' is 'VAGUER'.
'getting' is the link.
Can you help me to learn more?
(Other definitions for vaguer that I've seen before include "Less well defined" , "increasingly rough" .)