The most common and most likely answer to this crossword clue is the 5 plus 1 plus 2 letter word DRAWN - DD
D
R
A
W
N
-
D
D
Buddy explains!
The straight part
We know that "Strained/having produced sketch" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case strained/having produced sketch = drawn - dd.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.