The most common and most likely answer to this crossword clue is the 3 plus 4 letter word NEW TOWN
I've seen this crossword clue in The Sunday Telegraph
N
E
W
T
O
W
N
More clues leading to the result NEW TOWN
- Scientist drinking whiskey in Harlow?
- Old mathematician embracing wife in Milton Keynes, perhaps
- Force unit to seal off West Crawley, perhaps
- Dissident went and won Hemel Hempstead?
- Scientist accommodating wife in Basildon, say?
- Mathematician coming across wife in Harlow perhaps
- Little beast’s personal garden city?
- Unused to outskirts of Welwyn Garden City?
- Scientist has week probing modern community
- Won't create a planned urban community
Buddy explains!

The straight part
We know that "Basildon, say?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case basildon, say? = new town.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.