French mark I called squiggly (7)
I believe the answer is:
cedilla
'french mark' is the definition.
(I've seen this before)
'i called squiggly' is the wordplay.
'squiggly' is an anagram indicator.
'i'+'called'='icalled'
'icalled' anagrammed gives 'CEDILLA'.
(Other definitions for cedilla that I've seen before include "Mark suggesting a 'c' should be pronounced an 's'" , "The mark under the letter C in Spanish" , "Mark used under a c" , "Mark under the letter C in French" , "foreign accent" .)