Old boy's on unlimited notice to support Queen -- it's automatic (7)
I believe the answer is:
robotic
'automatic' is the definition.
(I've seen this before)
'old boy's on unlimited notice to support queen' is the wordplay.
'old boy' becomes 'ob'.
'on' means one lot of letters go next to another.
'unlimited' means to look at the middle letters (discard the edges or 'limits' of the word).
'to support' means one lot of letters go next to another.
'queen' becomes 'r' (r is abbreviation regina. e.g. in ER ).
The centre of 'notice' is 'otic'.
'ob'+'otic' is 'obotic'.
'obotic' after 'r' is 'ROBOTIC'.
'it's' acts as a link.
(Other definitions for robotic that I've seen before include "working mechanically" , "Of mechanical movements" , "Like a mechanical man" , "Mechanistic" , "Man made" .)