Old-fashioned when receiving short order and seriously committed (9)
I believe the answer is:
dedicated
'seriously committed' is the definition.
'dedicated' can be an answer for 'committed' (similar in meaning). I'm not sure about the 'seriously' bit.
'old-fashioned when receiving short order' is the wordplay.
'old fashioned' becomes 'dated' (I've seen this before).
'when receiving' means one lot of letters goes inside another.
'short' means to remove the last letter.
'order' becomes 'edict' (synonyms).
'edict' with its final letter taken off is 'edic'.
'dated' placed around 'edic' is 'DEDICATED'.
'and' is the link.
Can you help me to learn more?
(Other definitions for dedicated that I've seen before include "Committed" , "Devoted to a particular cause or purpose" , "Devoted to a cause or ideal 99)" , "Diligent" , "Consecrated - single-minded" .)