Drop of tea lacking flavour - little change (5)
I believe the answer is:
tweak
'little change' is the definition.
'drop of tea lacking flavour' is the wordplay.
'drop of' indicates taking the first letters.
'lacking flavour' becomes 'weak'.
The first letter of 'tea' is 't'.
't'+'weak'='TWEAK'
(Other definitions for tweak that I've seen before include "Minor change" , "Pinch and twist" , "Slightly shift" , "Make a slight adjustment" , "spin, thus?" .)