Once an MoD highflier, pub crackpot tackles complex algebra (7,7)
I believe the answer is:
barrage balloon
'once an mod highflier' is the definition.
I can't judge whether this definition defines the answer.
'pub crackpot tackles complex algebra' is the wordplay.
'pub' becomes 'bar' (both are drinking establishments).
'crackpot' becomes 'loon' (I've seen this in another clue).
'tackles' is an insertion indicator (tackle can mean to intercept or surround).
'complex' indicates anagramming the letters.
'bar'+'loon'='barloon'
'algebra' with letters rearranged gives 'ragebal'.
'barloon' enclosing 'ragebal' is 'BARRAGE BALLOON'.
Can you help me to learn more?
(Other definitions for barrage balloon that I've seen before include "gets raised in self-defence" , "Deterrent to low-flying air attacks" .)