American energy - not quite so ineffective (7)
I believe the answer is:
useless
'quite so ineffective' is the definition.
'useless' can be an answer for 'ineffective' (associated in meaning). I'm not certain of the 'quite so' bit.
'american energy not' is the wordplay.
'american' becomes 'US' (United States).
'energy' becomes 'e' (physics symbol as in E=mc2).
'not' becomes 'less' (I've seen this in other clues).
'us'+'e'+'less'='USELESS'
Can you help me to learn more?
(Other definitions for useless that I've seen before include "Is Sue less impractical?" , "Counterproductive" , "Ineffective" , "Worth zilch" , "Not worth a jot" .)