Lower construction of French base (6)
I believe the answer is:
demean
'lower construction' is the definition.
'demean' can be an answer for 'lower' (I've seen this in another clue). I am not sure about the 'construction' bit.
'of french base' is the wordplay.
'of french' becomes 'de' ('of' in French).
'base' becomes 'mean' (synonyms).
'de'+'mean'='DEMEAN'
Can you help me to learn more?
(Other definitions for demean that I've seen before include "Discredit" , "Cause to lose respect" , "'Put down, degrade (6)'" , "Cause (someone) to lose dignity" , "Debase" .)