Think the chaps at the outside are having fun (9)
I believe the answer is:
amusement
'fun' is the definition.
(thesaurus)
'think the chaps at the outside' is the wordplay.
'think' becomes 'muse' (musing is a kind of thinking**).
'the chaps' becomes 'men' (I've seen this before).
'the outside' indicates putting letters inside.
'muse'+'men'='musemen'
'musemen' placed inside 'at' is 'AMUSEMENT'.
'are having' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for amusement that I've seen before include "Pastime; recreation" , "enjoyment for 19 > [(type of) PARK]" , "Diversion, recreation" , "Pleasure, diversion" , "Entertainment" .)