Bother an engineer in love (5)
I believe the answer is:
adore
'love' is the definition.
(adoring is a kind of loving)
'bother an engineer' is the wordplay.
'bother' becomes 'ado' (I've seen this before).
'an engineer' becomes 're' (Royal Engineer).
'ado'+'re'='ADORE'
'in' is the link.
(Other definitions for adore that I've seen before include "Love to distraction" , "Love greatly" , "Treasure" , "Love, worship" , "Cherish" .)