Colin worried about keys being short (7)
I believe the answer is:
laconic
'short' is the definition.
(synonyms)
'colin worried about keys' is the wordplay.
'worried' indicates an anagram (worry can mean to interfere with or disturb).
'about' is an insertion indicator.
'keys' becomes 'ac' (I can't explain this - if you can you should believe this answer much more).
'colin' is an anagram of 'lonic'.
'lonic' enclosing 'ac' is 'LACONIC'.
'being' is the link.
Can you help me to learn more?
(Other definitions for laconic that I've seen before include "Terse, brief of speech" , "Saying few words" , "Spartan" , "with little expression" , "Conical (anag) -- brief and to the point" .)