Catch the sun and keep complaining about it (4)
I believe the answer is:
snag
'catch the sun' is the definition.
'snag' can be an answer for 'catch' (snagging is a kind of catching). I'm unsure of the 'the sun' bit.
'and keep complaining about it' is the wordplay.
'and' becomes 'n' (common abbreviation for 'and').
'keep complaining' becomes 'sag' (I can't justify this - if you can you should believe this answer much more).
'about it' indicates putting letters inside (some letters go around or about others).
'n' placed within 'sag' is 'SNAG'.
Can you help me to learn more?
(Other definitions for snag that I've seen before include "Glitch" , "A hidden or unexpected obstacle" , "Rip or tear" , "Hitch, obstacle" , "Catch -- problem" .)