The most common and most likely answer to this crossword clue is the 6 letter word GAMBIT
I've seen this crossword clue in The Daily Telegraph
G
A
M
B
I
T
More clues leading to the result GAMBIT
- Good scope offered by opening on board
- Chess move took effect after most of match
- Doctor taking walk round reveals stratagem
- Clever opening of golf range
- Good scope offered by initial moves
- Good scope for manoeuvre
- Over half of games sample plan
- “Sacrifice Green’s head!”: morning piece
- Initial strategy to take over journal had an impact
- Game sacrifice of good compass
Buddy explains!

The straight part
We know that "Tactic" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case tactic = gambit.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 GAMBIT mean?
GAMBIT noun- An opening in chess, in which a minor piece or a pawn is sacrificed to gain an advantage.
- Any ploy or stratagem.
- A remark intended to open a conversation.
- To sacrifice (a pawn or minor piece) to gain an advantage.