Strange French article found on us initially upset a learner (7)
I believe the answer is:
unusual
'strange' is the definition.
(I know that strange can be written as unusual)
'french article found on us initially upset a learner' is the wordplay.
'french article' becomes 'un' (indefinite article in French).
'found on' says to put letters next to each other.
'initially' suggests taking the first letters.
'learner' becomes 'l' (as in a learner driver with L-plates on their car).
The initial letter of 'upset' is 'u'.
'un'+'us'+'u'+'a'+'l'='UNUSUAL'
(Other definitions for unusual that I've seen before include "Peculiar" , "Not commonly encountered" , "Not normal, strange" , "Not habitually or commonly occurring" , "Extraordinary!" .)