Really pleased with flowers, half missing (4)
I believe the answer is:
glad
'really pleased' is the definition.
'glad' can be an answer for 'pleased' (similar in meaning). I'm not certain of the 'really' bit.
'flowers half missing' is the wordplay.
'flowers' becomes 'gladioli' (I've seen this before).
'half missing' indicates taking half.
'gladioli' cut in half is 'GLAD'.
'with' is the link.
Can you help me to learn more?
(Other definitions for glad that I've seen before include "Joyful" , "Made up" , "Not sorry" , "bright?" , "Happy, cheerful" .)