In the main imbibing contents of clouds (5)
I believe the answer is:
nimbi
'clouds' is the definition.
(nimbus is a kind of cloud)
'in the main imbibing contents' is the wordplay.
'in' says the answer is hidden in the clue.
'NIMBI' can be found hidden inside 'main imbibing contents'.
'of' acts as a link.
(Other definitions for nimbi that I've seen before include "They may surround the head" , "Rain clouds - halos" , "rings" , "Dark things" , "Rain-bearing clouds" .)