The most common and most likely answer to this crossword clue is the 7 letter word RELATED
I've seen this crossword clue in Independent
R
E
L
A
T
E
D
More clues leading to the result RELATED
- Covered by revolutionary, story in retrospect told
- Joker finally in euphoric state, as the Marx Brothers were
- Recently clothed in bright colour - as mother and daughter are
- Connected new treadle
- Told story about boring revolutionary
- King’s happy to be of he same family
- Told to raise the spirits, in a way
- Part of the family, as is told
- Members of a family are told
- King overjoyed when told
Buddy explains!

The straight part
We know that "Da and I are" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case da and i are = related.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does RELATED mean?
RELATED verb- To tell in a descriptive way.
- To bring into a relation, association, or connection (between one thing and another).
- To have a connection.
- To interact.
- To respond through reaction.
- (with to) To identify with; to understand.
- To bring back; to restore.
- Standing in relation or connection.
- Being a relative of.
- Narrated; told.
- Fulfilling a relation.
- (in combination) Having a relationship with the thing named
- Connected to or depending on something else; comparative.
- (of a URL, URI, path, or similar) Expressed in relation to another item, rather than in complete form.
- (grammar) That relates to an antecedent.
- Having the same key but differing in being major or minor.
- Relevant; pertinent; related.
- Capable to be changed by other beings or circumstance; conditional.