Determined to be a worker on embankment (7)
I believe the answer is:
adamant
'determined' is the definition.
(I've seen this before)
'a worker on embankment' is the wordplay.
'worker' becomes 'ant' (worker is a type of ant).
'on' is a charade indicator (letters next to each other).
'embankment' becomes 'dam' (I've seen this before).
'ant' after 'dam' is 'damant'.
'a'+'damant'='ADAMANT'
'to be' acts as a link.
(Other definitions for adamant that I've seen before include "Resolute, refusing to yield" , "Decided" , "Definite and unyielding" , "Unshakable (in an opinion)" , "intractable" .)