Hard work and energy will yield expectation (4)
I believe the answer is:
hope
'yield expectation' is the definition.
'hope' can be an answer for 'expectation' (hope is a kind of expectation). I am not sure about the 'yield' bit.
'hard work and energy' is the wordplay.
'hard' becomes 'h' (abbreviation used in pencil classifications).
'work' becomes 'op' (common abbreviation for 'opus').
'and' means one lot of letters go next to another.
'energy' becomes 'e' (physics symbol as in E=mc2).
'h'+'op'+'e'='HOPE'
'will' is the link.
Can you help me to learn more?
(Other definitions for hope that I've seen before include "It alone stayed in Pandora's box" , "Longing" , "Feeling of expectant desire" , "English-born US comedian, d. 2003" , "confidence" .)