The most common and most likely answer to this crossword clue is the 9 letter word ECTOMORPH
I've seen this crossword clue in The Daily Telegraph
E
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More clues leading to the result ECTOMORPH
Buddy explains!

The straight part
We know that "Delicately built type" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case delicately built type = ectomorph.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 ECTOMORPH mean?
ECTOMORPH noun- Someone with a lean, only slightly muscular body
- : Theoretical body type in which a person has a high metabolism. Such a person can easily maintain a low fat physique, but does not add muscle or body weight easily.