Inter perhaps when lifeless (5)
I believe the answer is:
inert
'lifeless' is the definition.
(I've seen this in another clue)
'inter perhaps' is the wordplay.
'perhaps' is an anagram indicator.
'inter' with letters rearranged gives 'INERT'.
'when' acts as a link.
(Other definitions for inert that I've seen before include "Devoid of motion or change" , "Slow and apathetic" , "lazy" , "Lifeless; apathetic" , "Sluggish, inactive" .)