Feeble type felt regularly full of expressionless misery (3,7)
I believe the answer is:
wet blanket
'misery' is the definition.
(I've seen this before)
'feeble type felt regularly full of expressionless' is the wordplay.
'feeble type' becomes 'wet' (informal term for a feeble person).
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'full of' means one lot of letters goes inside another.
'expressionless' becomes 'blank' (I've seen this before).
The alternating letters of 'felt' are 'et'.
'wet'+'et'='wetet'
'wetet' placed around 'blank' is 'WET BLANKET'.
(Other definitions for wet blanket that I've seen before include "Depressing person with lack of spirit" , "Person spoiling others' pleasure" , "Spoilsport" , "what could moisten kippers" , "Killjoy" .)