A strike in work on the dam (6)
I believe the answer is:
wallop
'a strike' is the definition.
(I've seen this before)
'work on the dam' is the wordplay.
'work' becomes 'op' (operation, work done in an operating theatre).
'on' says to put letters next to each other.
'the dam' becomes 'wall' (I can't explain this - if you can you should give a lot more credence to this answer).
'op' put after 'wall' is 'WALLOP'.
'in' is the link.
Can you help me to learn more?
(Other definitions for wallop that I've seen before include "Alcoholic drink" , "buffet?" , "Beat" , "Strike very hard" , "Hit - the booze?" .)