The most common and most likely answer to this crossword clue is the 8 letter word OUTFIELD
I've seen this crossword clue in The Daily Telegraph
O
U
T
F
I
E
L
D
Buddy explains!
The straight part
We know that "the deep" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case the deep = outfield.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 OUTFIELD mean?
OUTFIELD noun- The region of the field between the infield and the outer fence.
- The region of the field roughly outside of the infield or the wicket-keeper, slips, gully, point, cover, mid off, mid on, midwicket and square leg.
- Arable land continually cropped without being manured.
- Any open field at a distance from the farmsteading.
- To perform better in defense (fielding).