They don't worry the steeple jack - he has bad sight (7)
I believe the answer is:
heights
'they don't worry the steeple jack he has bad sight' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'he has bad sight' is the wordplay.
'has' is a charade indicator (letters next to each other).
'bad' indicates an anagram.
'sight' with letters rearranged gives 'ights'.
'he'+'ights'='HEIGHTS'
Can you help me to learn more?
(Other definitions for heights that I've seen before include "High places" , "Peaks" , "See 23 ac" , "Distances from top to bottom" , "Summits" .)