Crossword Genius

Efficient, therefore negative with Frenchman in charge (9)

Ross

I believe the answer is:

ergonomic

I'm a little stuck... Click here to teach me more about this clue!

'efficient' is the definition.
Both the answer and definition are adjectives.
Maybe there's a link between them I don't understand?

'therefore negative with frenchman in charge' is the wordplay.
'therefore' becomes 'ergo' (I've seen this before).
'negative' becomes 'no' (no is a kind of negative).
'with' is a charade indicator (letters next to each other).
'frenchman' becomes 'm' (abbreviation for Monsieur - like 'Mr').
'in charge' becomes 'ic' (abbreviation for 'in charge').
'ergo'+'no'+'m'+'ic'='ERGONOMIC'

Can you help me to learn more?

(Other definitions for ergonomic that I've seen before include "Maximising efficiency" , "operating with maximum efficiency" , "Designed for efficiency and comfort in the working environment" , "using biotechnology" , "Designed for work efficiency" .)

I've seen this clue in The Daily Express.
Want a hint initially instead of a full solution? Install my app