Fill in rowing crew about northern lake in French (9)
I believe the answer is:
enlighten
'fill in' is the definition.
The answer and definition can be both to do with communicating as well as being verbs in their base form.
Maybe they are linked in a way I don't understand?
'rowing crew about northern lake in french' is the wordplay.
'rowing crew' becomes 'eight' (a crew of eight rowers is called an 'eight').
'about' is an insertion indicator.
'northern' becomes 'n' (abbreviation e.g. N. Ireland).
'lake' becomes 'L' (geographical abbreviation).
'in french' becomes 'en' ('in' in French).
'n'+'l'='nl'
'eight' placed around 'nl' is 'enlight'.
'enlight'+'en'='ENLIGHTEN'
Can you help me to learn more?
(Other definitions for enlighten that I've seen before include "Give instruction" , "Free from ignorance" , "Illuminate" , "remove prejudice" , "Explain" .)