Offering no problems when probing limits of energy (4)
I believe the answer is:
easy
'offering no problems when probing limits of energy' is the definition.
I can't tell whether this definition defines the answer.
'when probing limits of energy' is the wordplay.
'when' becomes 'as' (eg 'when I walked' means 'as I walked').
'probing' is an insertion indicator (probe can mean to make a hole in).
'limits of' suggests removing the centre.
'energy' with its middle taken out is 'ey'.
'as' inserted into 'ey' is 'EASY'.
Can you help me to learn more?
(Other definitions for easy that I've seen before include "Facile" , "in plentiful supply" , "Simple (like the living in 1 across)" , "Posing no difficulty" , "for a piece of cake" .)