Second skin returning for a period, having dropped off (5)
I believe the answer is:
sleep
'second skin' is the definition.
The definition and answer can be both related to time as well as being singular nouns.
Perhaps there's a link between them I don't understand?
'returning for a period having dropped off' is the wordplay.
'returning for' becomes 'slee' (I am not sure about this - if you are sure you should believe this answer much more).
'a' becomes 'amp' (A is the symbol for the amp or ampere).
'period' becomes 'A.M.' (A.M. is an example).
'having dropped off' suggests deleting specific letters.
'amp' with 'am' taken away is 'p'.
'slee'+'p'='SLEEP'
Can you help me to learn more?
(Other definitions for sleep that I've seen before include "Be dormant" , "Drop off" , "crash" , "Doze, nap" , "Shut-eye" .)