Fed up with hesitation, postpone action (5)
I believe the answer is:
defer
'postpone action' is the definition.
'defer' can be an answer for 'postpone' (synonyms). I'm not certain of the 'action' bit.
'fed up with hesitation' is the wordplay.
'up' says the letters should be written backwards (in down clue: letters go upwards).
'with' means one lot of letters go next to another.
'hesitation' becomes 'er' (sound made while hesitating - um, er).
'fed' written backwards gives 'def'.
'def'+'er'='DEFER'
Can you help me to learn more?
(Other definitions for defer that I've seen before include "Put off to later time" , "Postpone or yield to another" , "Put off till later" , "stall" , "Delay" .)