Travelling comedian strangely lacking in energy (7)
I believe the answer is:
nomadic
'travelling' is the definition.
(I've seen this before)
'comedian strangely lacking in energy' is the wordplay.
I cannot really understand how this works, but
'lacking' could be 'no' (eg lacking money means with no money) and 'no' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for nomadic that I've seen before include "Perhaps unsettling" , "Not settled" , "migrant" , "Migratory" , "Homeless - wandering" .)