One fluid in another, it seems to me (8)
I believe the answer is:
methinks
'one fluid in another it' is the definition.
I can't judge whether this defines the answer.
'seems to me' is the wordplay.
'seems' becomes 'thinks' (I am not sure about this - if you are sure you should believe this answer much more).
'to' is a charade indicator (letters next to each other) (I've seen this in other clues).
'thinks' after 'me' is 'METHINKS'.
Can you help me to learn more?
(Other definitions for methinks that I've seen before include "I believe" , "I gather" , "I reckon" , "In my view - knit hems (anag)" , "I feel ..." .)