Ineffectual person, this writer the French avoid locking up (4,4)
I believe the answer is:
lame duck
'ineffectual person' is the definition.
(I've seen this before)
'this writer the french avoid locking up' is the wordplay.
'this writer' becomes 'me' (the person who is writing these clues).
'the french' becomes 'la'.
'avoid' becomes 'duck' (ducking is a kind of avoiding).
'locking up' indicates putting letters inside.
'la'+'duck'='laduck'
'me' going inside 'laduck' is 'LAME DUCK'.
(Other definitions for lame duck that I've seen before include "Feeble person" , "Inefficient or helpless person" , "Wimp" , "not an effective official - with 20d" , "does one need help from PDSA?" .)