Army doctor has wobbly about decorative design (5)
I believe the answer is:
motif
'decorative design' is the definition.
(I've seen this before)
'army doctor has wobbly about' is the wordplay.
'army doctor' becomes 'mo' (medical officer).
'has' says to put letters next to each other.
'wobbly' becomes 'fit' (both can mean a tantrum).
'about' says the letters should be written in reverse.
'fit' in reverse letter order is 'tif'.
'mo'+'tif'='MOTIF'
(Other definitions for motif that I've seen before include "Recurring image in design" , "Distinctive idea or theme" , "Recurring theme, especially in music" , "decoration" , "Recurring theme in musical work" .)