The first feeble change (5)
I believe the answer is:
tweak
'change' is the definition.
(I've seen this before)
'the first feeble' is the wordplay.
'the first' becomes 't' (wst letter of 'the').
'feeble' becomes 'weak' (similar in meaning).
't'+'weak'='TWEAK'
(Other definitions for tweak that I've seen before include "Improve (something) by fine adjustments" , "Fine-tune, twist" , "Twist; adjust finely" , "Make small adjustment" , "Make a slight adjustment" .)