This might hold oil like fish contains (5)
I believe the answer is:
easel
'this might hold oil' is the definition.
Although both the answer and definition are singular nouns, I can't understand how one could define the other.
'like fish contains' is the wordplay.
'like' becomes 'as'.
'fish' becomes 'eel' (eel is a type of fish).
'contains' indicates putting letters inside.
'as' inserted inside 'eel' is 'EASEL'.
Can you help me to learn more?
(Other definitions for easel that I've seen before include "The rest of artists" , "Artist's canvas suppot" , "the rest of the paintwork" , "Support for artist's canvas" , "Painter's stand" .)