Felt these bats circling area -- they often come out at night (5,5)
I believe the answer is:
false teeth
'they often come out at night' is the definition.
(I've seen this in another clue)
'felt these bats circling area' is the wordplay.
'bats' indicates anagramming the letters (slang for mad).
'circling' indicates putting letters inside (circling can mean going around or containing).
'area' becomes 'a' (maths abbreviation).
'felt'+'these'='feltthese'
'feltthese' anagrammed gives 'flseteeth'.
'flseteeth' placed around 'a' is 'FALSE TEETH'.
(Other definitions for false teeth that I've seen before include "Choppers that may be taken out" , "New gnashers!" , "set out at night" , "Plates" , "Denture's components" .)