Again not fully crossing the dam (6)
I believe the answer is:
mother
'dam' is the definition.
(thesaurus)
'again not fully crossing the' is the wordplay.
'again' becomes 'more' (I've seen this in other clues).
'not fully' means to remove the last letter.
'crossing' indicates putting letters inside.
'more' with its last letter taken away is 'mor'.
'mor' placed around 'the' is 'MOTHER'.
(Other definitions for mother that I've seen before include "Be overprotective" , "She gave birth to her Tom" , "- - 7 across, pantomime" , "Dam" , "Nature so-called" .)