The most common and most likely answer to this crossword clue is the 5 letter word INERT
I've seen this crossword clue in The Guardian
I
N
E
R
T
More clues leading to the result INERT
- I rent, poor and lazy
- Spin around, lacking velocity still
- Still awkward to see Penny turning Republican
- Immobile excavator losing motorway time
- Lying motionless in bed, having removed clothing
- Passive passage from Sartre nicely recalled
- Like some gases examiner tests partly
- Not reactive or interactive
- Still at home, regret regularly missing out
- With temperature dropping, bury dead
Buddy explains!

The straight part
We know that "Disinclined" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case disinclined = inert.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 INERT mean?
INERT noun- A substance that does not react chemically.
- To fill with an inert gas to reduce the risk of explosion.
- Unable to move or act; inanimate.
- In chemistry, not readily reacting with other elements or compounds.
- Having no therapeutic action.