Diffident means less than pushy (3)
I believe the answer is:
shy
'diffident' is the definition.
('shy' can be a synonym of 'diffident')
'less than pushy' is the wordplay.
'SHY' is hidden within the letters.
However, I am unsure how the hidden word is indicated.
'means' acts as a link.
Can you help me to learn more?
(Other definitions for shy that I've seen before include "'Timid, diffident (3)'" , "Timid (around people)" , "Pitch" , "Reticent" , "Timid and self-conscious" .)