Acerbic worker, say, beside dyke (9)
I believe the answer is:
trenchant
'acerbic' is the definition.
(I've seen this before)
'worker say beside dyke' is the wordplay.
'worker say' becomes 'ant' (worker is a type of ant).
'beside' is a charade indicator (letters next to each other) (I've seen this in other clues).
'dyke' becomes 'trench' (I can't justify this - if you can you should give a lot more credence to this answer).
'ant' after 'trench' is 'TRENCHANT'.
Can you help me to learn more?
(Other definitions for trenchant that I've seen before include "Vigorous, incisive" , "Clear" , "Incisive in style" , "Showing keenness" , "caustic?" .)