Like complex gadgets, with problem conserving energy (2-4)
I believe the answer is:
hi-tech
'like complex gadgets with' is the definition.
I can't tell whether this defines the answer.
'problem conserving energy' is the wordplay.
'problem' becomes 'hitch' (a hitch is a problem or difficulty).
'conserving' is an insertion indicator.
'energy' becomes 'e' (physics symbol as in E=mc2).
'hitch' enclosing 'e' is 'HI-TECH'.
Can you help me to learn more?
(Other definitions for hi-tech that I've seen before include "(Using) the latest developments" , "latest devices" , "Advanced technology" , "Involving the latest electronic gadgetry" , "Style of interior design using features of industrial equipment" .)