Attentive husband occasionally found out — slippery character to catch! (7)
I believe the answer is:
heedful
'attentive' is the definition.
(heedful can mean listening or paying attention)
'husband occasionally found out slippery character to catch' is the wordplay.
'husband' becomes 'h' ().
'occasionally' means one should take alternating letters.
'out' indicates an anagram (out can mean wrong or inaccurate).
'slippery character' becomes 'eel' (slippery fish).
'to catch' means one lot of letters goes inside another.
The alternating letters of 'found' are 'fud'.
'fud' anagrammed gives 'dfu'.
'dfu' going into 'eel' is 'eedful'.
'h'+'eedful'='HEEDFUL'
(Other definitions for heedful that I've seen before include "Attentive - circumspect" , "Paying careful attention" , "Attentive, listening carefully" , "Wary" , "Prudent" .)